diff --git a/apps/dav/lib/CalDAV/Schedule/IMipPlugin.php b/apps/dav/lib/CalDAV/Schedule/IMipPlugin.php
index ffe6930fdb4a..4fcbc95e535e 100644
--- a/apps/dav/lib/CalDAV/Schedule/IMipPlugin.php
+++ b/apps/dav/lib/CalDAV/Schedule/IMipPlugin.php
@@ -41,21 +41,12 @@
  * @license http://sabre.io/license/ Modified BSD License
  */
 class IMipPlugin extends SabreIMipPlugin {
-	/** @var IMailer */
-	private $mailer;
-
-	/** @var ILogger */
-	private $logger;
-
-	/** @var IRequest */
-	private $request;
+	private IMailer $mailer;
+	private ILogger $logger;
+	private IRequest $request;
 
 	/**
 	 * Creates the email handler.
-	 *
-	 * @param IMailer $mailer
-	 * @param ILogger $logger
-	 * @param IRequest $request
 	 */
 	public function __construct(IMailer $mailer, ILogger $logger, IRequest $request) {
 		parent::__construct('');
@@ -123,14 +114,10 @@ public function schedule(ITip\Message $iTipMessage) {
 			->setFrom([$sender => $senderName])
 			->setTo([$recipient => $recipientName])
 			->setSubject($subject)
-			->setBody($iTipMessage->message->serialize(), $contentType);
+			->attach($iTipMessage->message->serialize(), "event.ics", $contentType);
 		try {
-			$failed = $this->mailer->send($message);
+			$this->mailer->send($message);
 			$iTipMessage->scheduleStatus = '1.1; Scheduling message is sent via iMip';
-			if ($failed) {
-				$this->logger->error('Unable to deliver message to {failed}', ['app' => 'dav', 'failed' =>  \implode(', ', $failed)]);
-				$iTipMessage->scheduleStatus = '5.0; EMail delivery failed';
-			}
 		} catch (\Exception $ex) {
 			$this->logger->logException($ex, ['app' => 'dav']);
 			$iTipMessage->scheduleStatus = '5.0; EMail delivery failed';
diff --git a/apps/dav/tests/unit/CalDAV/Schedule/IMipPluginTest.php b/apps/dav/tests/unit/CalDAV/Schedule/IMipPluginTest.php
index c1902456caab..534cd97253e0 100644
--- a/apps/dav/tests/unit/CalDAV/Schedule/IMipPluginTest.php
+++ b/apps/dav/tests/unit/CalDAV/Schedule/IMipPluginTest.php
@@ -22,124 +22,78 @@
 
 namespace OCA\DAV\Tests\unit\CalDAV\Schedule;
 
+use Exception;
 use OC\Mail\Mailer;
 use OCA\DAV\CalDAV\Schedule\IMipPlugin;
 use OCP\ILogger;
 use OCP\IRequest;
+use PHPUnit\Framework\MockObject\MockObject;
 use Sabre\VObject\Component\VCalendar;
 use Sabre\VObject\ITip\Message;
+use Symfony\Component\Mime\Email;
 use Test\TestCase;
 use OC\Log;
 
 class IMipPluginTest extends TestCase {
-	public function testDelivery() {
-		$mailMessage = new \OC\Mail\Message(new \Swift_Message());
-		/** @var Mailer | \PHPUnit\Framework\MockObject\MockObject $mailer */
-		$mailer = $this->createMock(Mailer::class);
-		$mailer->method('createMessage')->willReturn($mailMessage);
-		$mailer->expects($this->once())->method('send');
-		/** @var ILogger | \PHPUnit\Framework\MockObject\MockObject $logger */
-		$logger = $this->createMock(Log::class);
-		/** @var IRequest| \PHPUnit\Framework\MockObject\MockObject $request */
+	private \OC\Mail\Message $mailMessage;
+	/**
+	 * @var Mailer|MockObject
+	 */
+	private $mailer;
+	private IMipPlugin $plugin;
+	/** @var ILogger|MockObject */
+	private $logger;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->mailMessage = new \OC\Mail\Message(new Email());
+		$this->mailer = $this->createMock(Mailer::class);
+		$this->mailer->method('createMessage')->willReturn($this->mailMessage);
+
+		$this->logger = $this->createMock(Log::class);
+		/** @var IRequest| MockObject $request */
 		$request = $this->createMock(IRequest::class);
 
-		$plugin = new IMipPlugin($mailer, $logger, $request);
-		$message = new Message();
-		$message->method = 'REQUEST';
-		$message->message = new VCalendar();
-		$message->message->add('VEVENT', [
-			'UID' => $message->uid,
-			'SEQUENCE' => $message->sequence,
-			'SUMMARY' => 'Fellowship meeting',
-		]);
-		$message->sender = 'mailto:gandalf@wiz.ard';
-		$message->recipient = 'mailto:frodo@hobb.it';
+		$this->plugin = new IMipPlugin($this->mailer, $this->logger, $request);
+	}
+
+	public function testDelivery(): void {
+		$this->mailer->expects($this->once())->method('send');
+
+		$message = $this->buildIMIPMessage('REQUEST');
 
-		$plugin->schedule($message);
+		$this->plugin->schedule($message);
 		$this->assertEquals('1.1', $message->getScheduleStatus());
-		$this->assertEquals('Fellowship meeting', $mailMessage->getSubject());
-		$this->assertEquals(['frodo@hobb.it' => null], $mailMessage->getTo());
-		$this->assertEquals(['gandalf@wiz.ard' => null], $mailMessage->getReplyTo());
-		$this->assertEquals('text/calendar; charset=UTF-8; method=REQUEST', $mailMessage->getSwiftMessage()->getContentType());
+		$this->assertEquals('Fellowship meeting', $this->mailMessage->getSubject());
+		$this->assertEquals(['frodo@hobb.it' => null], $this->mailMessage->getTo());
+		$this->assertEquals(['gandalf@wiz.ard' => null], $this->mailMessage->getReplyTo());
+		$this->assertStringContainsString('text/calendar; charset=UTF-8; method=REQUEST', $this->mailMessage->getMessage()->getBody()->bodyToString());
 	}
 
-	public function testFailedDeliveryWithException() {
-		$mailMessage = new \OC\Mail\Message(new \Swift_Message());
-		/** @var Mailer | \PHPUnit\Framework\MockObject\MockObject $mailer */
-		$mailer = $this->createMock(Mailer::class);
-		$mailer->method('createMessage')->willReturn($mailMessage);
-		$mailer->method('send')->willThrowException(new \Exception());
-		/** @var ILogger | \PHPUnit\Framework\MockObject\MockObject $logger */
-		$logger = $this->createMock(Log::class);
-		/** @var IRequest| \PHPUnit\Framework\MockObject\MockObject $request */
-		$request = $this->createMock(IRequest::class);
+	public function testFailedDeliveryWithException(): void {
+		$ex = new Exception();
+		$this->mailer->method('send')->willThrowException($ex);
+		$this->logger->expects(self::once())->method('logException')->with($ex, ['app' => 'dav']);
 
-		$plugin = new IMipPlugin($mailer, $logger, $request);
-		$message = new Message();
-		$message->method = 'REQUEST';
-		$message->message = new VCalendar();
-		$message->message->add('VEVENT', [
-			'UID' => $message->uid,
-			'SEQUENCE' => $message->sequence,
-			'SUMMARY' => 'Fellowship meeting',
-		]);
-		$message->sender = 'mailto:gandalf@wiz.ard';
-		$message->recipient = 'mailto:frodo@hobb.it';
+		$message = $this->buildIMIPMessage('REQUEST');
 
-		$plugin->schedule($message);
-		$this->assertEquals('5.0', $message->getScheduleStatus());
-		$this->assertEquals('Fellowship meeting', $mailMessage->getSubject());
-		$this->assertEquals(['frodo@hobb.it' => null], $mailMessage->getTo());
-		$this->assertEquals(['gandalf@wiz.ard' => null], $mailMessage->getReplyTo());
-		$this->assertEquals('text/calendar; charset=UTF-8; method=REQUEST', $mailMessage->getSwiftMessage()->getContentType());
+		$this->plugin->schedule($message);
+		$this->assertIMipState($message, '5.0', 'REQUEST', 'Fellowship meeting');
 	}
 
-	public function testFailedDelivery() {
-		$mailMessage = new \OC\Mail\Message(new \Swift_Message());
-		/** @var Mailer | \PHPUnit\Framework\MockObject\MockObject $mailer */
-		$mailer = $this->createMock(Mailer::class);
-		$mailer->method('createMessage')->willReturn($mailMessage);
-		$mailer->method('send')->willReturn(['foo@example.net']);
-		/** @var ILogger | \PHPUnit\Framework\MockObject\MockObject $logger */
-		$logger = $this->createMock(Log::class);
-		$logger->expects(self::once())->method('error')->with('Unable to deliver message to {failed}', ['app' => 'dav', 'failed' => 'foo@example.net']);
-		/** @var IRequest| \PHPUnit\Framework\MockObject\MockObject $request */
-		$request = $this->createMock(IRequest::class);
+	public function testDeliveryOfCancel(): void {
+		$this->mailer->expects($this->once())->method('send');
 
-		$plugin = new IMipPlugin($mailer, $logger, $request);
-		$message = new Message();
-		$message->method = 'REQUEST';
-		$message->message = new VCalendar();
-		$message->message->add('VEVENT', [
-			'UID' => $message->uid,
-			'SEQUENCE' => $message->sequence,
-			'SUMMARY' => 'Fellowship meeting',
-		]);
-		$message->sender = 'mailto:gandalf@wiz.ard';
-		$message->recipient = 'mailto:frodo@hobb.it';
+		$message = $this->buildIMIPMessage('CANCEL');
 
-		$plugin->schedule($message);
-		$this->assertEquals('5.0', $message->getScheduleStatus());
-		$this->assertEquals('Fellowship meeting', $mailMessage->getSubject());
-		$this->assertEquals(['frodo@hobb.it' => null], $mailMessage->getTo());
-		$this->assertEquals(['gandalf@wiz.ard' => null], $mailMessage->getReplyTo());
-		$this->assertEquals('text/calendar; charset=UTF-8; method=REQUEST', $mailMessage->getSwiftMessage()->getContentType());
+		$this->plugin->schedule($message);
+		$this->assertIMipState($message, '1.1', 'CANCEL', 'Cancelled: Fellowship meeting');
 	}
 
-	public function testDeliveryOfCancel() {
-		$mailMessage = new \OC\Mail\Message(new \Swift_Message());
-		/** @var Mailer | \PHPUnit\Framework\MockObject\MockObject $mailer */
-		$mailer = $this->createMock(Mailer::class);
-		$mailer->method('createMessage')->willReturn($mailMessage);
-		$mailer->expects($this->once())->method('send');
-		/** @var ILogger | \PHPUnit\Framework\MockObject\MockObject $logger */
-		$logger = $this->createMock(Log::class);
-		/** @var IRequest| \PHPUnit\Framework\MockObject\MockObject $request */
-		$request = $this->createMock(IRequest::class);
-
-		$plugin = new IMipPlugin($mailer, $logger, $request);
+	private function buildIMIPMessage(string $method): Message {
 		$message = new Message();
-		$message->method = 'CANCEL';
+		$message->method = $method;
 		$message->message = new VCalendar();
 		$message->message->add('VEVENT', [
 			'UID' => $message->uid,
@@ -148,13 +102,14 @@ public function testDeliveryOfCancel() {
 		]);
 		$message->sender = 'mailto:gandalf@wiz.ard';
 		$message->recipient = 'mailto:frodo@hobb.it';
+		return $message;
+	}
 
-		$plugin->schedule($message);
-		$this->assertEquals('1.1', $message->getScheduleStatus());
-		$this->assertEquals('Cancelled: Fellowship meeting', $mailMessage->getSubject());
-		$this->assertEquals(['frodo@hobb.it' => null], $mailMessage->getTo());
-		$this->assertEquals(['gandalf@wiz.ard' => null], $mailMessage->getReplyTo());
-		$this->assertEquals('text/calendar; charset=UTF-8; method=CANCEL', $mailMessage->getSwiftMessage()->getContentType());
-		$this->assertEquals('CANCELLED', $message->message->VEVENT->STATUS->getValue());
+	private function assertIMipState(Message $message, string $scheduleStatus, string $method, string $mailSubject): void {
+		$this->assertEquals($scheduleStatus, $message->getScheduleStatus());
+		$this->assertEquals($mailSubject, $this->mailMessage->getSubject());
+		$this->assertEquals(['frodo@hobb.it' => null], $this->mailMessage->getTo());
+		$this->assertEquals(['gandalf@wiz.ard' => null], $this->mailMessage->getReplyTo());
+		$this->assertStringContainsString("text/calendar; charset=UTF-8; method=$method", $this->mailMessage->getMessage()->getBody()->bodyToString());
 	}
 }
diff --git a/composer.json b/composer.json
index 78fb861248a4..ff77ab799f58 100644
--- a/composer.json
+++ b/composer.json
@@ -1,118 +1,118 @@
 {
-    "name": "owncloud/core",
-    "description": "A safe home for all your data",
-    "license": "AGPL-1.0",
-    "config" : {
-        "vendor-dir": "lib/composer",
-        "optimize-autoloader": true,
-        "classmap-authoritative": false,
-        "platform": {
-            "php": "7.4"
-        },
-        "allow-plugins": {
-            "bamarni/composer-bin-plugin": true,
-            "dg/composer-cleaner": true
-        }
+  "name": "owncloud/core",
+  "description": "A safe home for all your data",
+  "license": "AGPL-1.0",
+  "config" : {
+    "vendor-dir": "lib/composer",
+    "optimize-autoloader": true,
+    "classmap-authoritative": false,
+    "platform": {
+      "php": "7.4"
     },
-    "autoload" : {
-        "psr-4": {
-            "OC\\": "lib/private",
-            "OC\\Core\\": "core/",
-            "OC\\Settings\\": "settings/",
-            "OCP\\": "lib/public"
-        },
-        "classmap": ["lib/private/legacy"],
-        "files": [
-            "apps/files_external/lib/config.php"
-        ]
-
-    },
-    "autoload-dev" : {
-        "files": [
-            "tests/lib/TestCase.php"
-        ]
-    },
-    "require-dev": {
-        "bamarni/composer-bin-plugin": "^1.8",
-        "mikey179/vfsstream": "^1.6",
-        "phpunit/phpunit": "^9.5",
-        "roave/security-advisories": "dev-latest"
-    },
-    "require": {
-        "php": ">=7.4",
-        "ext-apcu": "*",
-        "ext-ctype": "*",
-        "ext-curl": "*",
-        "ext-exif": "*",
-        "ext-fileinfo": "*",
-        "ext-gd": "*",
-        "ext-iconv": "*",
-        "ext-imagick": "*",
-        "ext-intl": "*",
-        "ext-json": "*",
-        "ext-libxml": "*",
-        "ext-mbstring": "*",
-        "ext-memcached": "*",
-        "ext-pdo": "*",
-        "ext-posix": "*",
-        "ext-simplexml": "*",
-        "ext-zip": "*",
-        "bantu/ini-get-wrapper": "v1.0.1",
-        "christophwurst/id3parser": "^0.1.4",
-        "composer/semver": "^3.3",
-        "deepdiver/zipstreamer": "^2.0",
-        "dg/composer-cleaner": "^2.2",
-        "doctrine/dbal": "^2.13",
-        "firebase/php-jwt": "^6.8",
-        "google/apiclient": "^2.15",
-        "guzzlehttp/guzzle": "^7.7",
-        "icewind/smb": "^3.6",
-        "icewind/streams": "0.7.7",
-        "interfasys/lognormalizer": "^v1.0",
-        "laminas/laminas-inputfilter": "^2.21",
-        "laminas/laminas-servicemanager": "^3.17",
-        "laminas/laminas-validator": "^2.25",
-        "laravel/serializable-closure": "^1.3",
-        "league/flysystem": "^1.1",
-        "nikic/php-parser": "^4.15",
-        "owncloud/tarstreamer": "v2.1.0",
-        "pear/archive_tar": "1.4.14",
-        "pear/pear-core-minimal": "^v1.10",
-        "phpseclib/phpseclib": "^3.0",
-        "pimple/pimple": "^3.5",
-        "punic/punic": "^3.8",
-        "sabre/dav": "^4.4",
-        "sabre/http": "^5.1",
-        "sabre/vobject": "^4.5",
-        "swiftmailer/swiftmailer": "^6.3",
-        "symfony/console": "^5.4",
-        "symfony/event-dispatcher": "^5.4",
-        "symfony/process": "^5.4",
-        "symfony/routing": "^5.4",
-        "symfony/translation": "^5.4"
+    "allow-plugins": {
+      "bamarni/composer-bin-plugin": true,
+      "dg/composer-cleaner": true
+    }
+  },
+  "autoload" : {
+    "psr-4": {
+      "OC\\": "lib/private",
+      "OC\\Core\\": "core/",
+      "OC\\Settings\\": "settings/",
+      "OCP\\": "lib/public"
     },
-    "replace": {
-        "symfony/polyfill-ctype": "*",
-        "symfony/polyfill-iconv": "*",
-        "symfony/polyfill-intl-grapheme": "*",
-        "symfony/polyfill-intl-idn": "*",
-        "symfony/polyfill-intl-normalizer": "*",
-        "symfony/polyfill-mbstring": "*",
-        "symfony/polyfill-php72": "*",
-        "symfony/polyfill-php73": "*"
+    "classmap": ["lib/private/legacy"],
+    "files": [
+      "apps/files_external/lib/config.php"
+    ]
+
+  },
+  "autoload-dev" : {
+    "files": [
+      "tests/lib/TestCase.php"
+    ]
+  },
+  "require-dev": {
+    "bamarni/composer-bin-plugin": "^1.8",
+    "mikey179/vfsstream": "^1.6",
+    "phpunit/phpunit": "^9.5",
+    "roave/security-advisories": "dev-latest"
+  },
+  "require": {
+    "php": ">=7.4",
+    "ext-apcu": "*",
+    "ext-ctype": "*",
+    "ext-curl": "*",
+    "ext-exif": "*",
+    "ext-fileinfo": "*",
+    "ext-gd": "*",
+    "ext-iconv": "*",
+    "ext-imagick": "*",
+    "ext-intl": "*",
+    "ext-json": "*",
+    "ext-libxml": "*",
+    "ext-mbstring": "*",
+    "ext-memcached": "*",
+    "ext-pdo": "*",
+    "ext-posix": "*",
+    "ext-simplexml": "*",
+    "ext-zip": "*",
+    "bantu/ini-get-wrapper": "v1.0.1",
+    "christophwurst/id3parser": "^0.1.4",
+    "composer/semver": "^3.3",
+    "deepdiver/zipstreamer": "^2.0",
+    "dg/composer-cleaner": "^2.2",
+    "doctrine/dbal": "^2.13",
+    "firebase/php-jwt": "^6.8",
+    "google/apiclient": "^2.15",
+    "guzzlehttp/guzzle": "^7.7",
+    "icewind/smb": "^3.6",
+    "icewind/streams": "0.7.7",
+    "interfasys/lognormalizer": "^v1.0",
+    "laminas/laminas-inputfilter": "^2.21",
+    "laminas/laminas-servicemanager": "^3.17",
+    "laminas/laminas-validator": "^2.25",
+    "laravel/serializable-closure": "^1.3",
+    "league/flysystem": "^1.1",
+    "nikic/php-parser": "^4.15",
+    "owncloud/tarstreamer": "v2.1.0",
+    "pear/archive_tar": "1.4.14",
+    "pear/pear-core-minimal": "^v1.10",
+    "phpseclib/phpseclib": "^3.0",
+    "pimple/pimple": "^3.5",
+    "punic/punic": "^3.8",
+    "sabre/dav": "^4.4",
+    "sabre/http": "^5.1",
+    "sabre/vobject": "^4.5",
+    "symfony/console": "^5.4",
+    "symfony/event-dispatcher": "^5.4",
+    "symfony/mailer": "^5.4",
+    "symfony/process": "^5.4",
+    "symfony/routing": "^5.4",
+    "symfony/translation": "^5.4"
+  },
+  "replace": {
+    "symfony/polyfill-ctype": "*",
+    "symfony/polyfill-iconv": "*",
+    "symfony/polyfill-intl-grapheme": "*",
+    "symfony/polyfill-intl-idn": "*",
+    "symfony/polyfill-intl-normalizer": "*",
+    "symfony/polyfill-mbstring": "*",
+    "symfony/polyfill-php72": "*",
+    "symfony/polyfill-php73": "*"
+  },
+  "scripts": {
+    "pre-autoload-dump": "Google\\Task\\Composer::cleanup"
+  },
+  "extra": {
+    "bamarni-bin": {
+      "bin-links": false
     },
-    "scripts": {
-        "pre-autoload-dump": "Google\\Task\\Composer::cleanup"
+    "cleaner-ignore": {
+      "phpunit/phpunit": true
     },
-    "extra": {
-        "bamarni-bin": {
-            "bin-links": false
-        },
-        "cleaner-ignore": {
-            "phpunit/phpunit": true
-        },
-        "google/apiclient-services": [
-            "Drive"
-        ]
-    }
+    "google/apiclient-services": [
+      "Drive"
+    ]
+  }
 }
diff --git a/composer.lock b/composer.lock
index 2aa47439088a..b08904ec1d93 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "a05f0ad17290b0a59773026392b39fa7",
+    "content-hash": "949e22ab13538c7505cdb4307e2d9f35",
     "packages": [
         {
             "name": "bantu/ini-get-wrapper",
@@ -3742,82 +3742,6 @@
             },
             "time": "2023-06-28T12:56:05+00:00"
         },
-        {
-            "name": "swiftmailer/swiftmailer",
-            "version": "v6.3.0",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/swiftmailer/swiftmailer.git",
-                "reference": "8a5d5072dca8f48460fce2f4131fcc495eec654c"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/swiftmailer/swiftmailer/zipball/8a5d5072dca8f48460fce2f4131fcc495eec654c",
-                "reference": "8a5d5072dca8f48460fce2f4131fcc495eec654c",
-                "shasum": ""
-            },
-            "require": {
-                "egulias/email-validator": "^2.0|^3.1",
-                "php": ">=7.0.0",
-                "symfony/polyfill-iconv": "^1.0",
-                "symfony/polyfill-intl-idn": "^1.10",
-                "symfony/polyfill-mbstring": "^1.0"
-            },
-            "require-dev": {
-                "mockery/mockery": "^1.0",
-                "symfony/phpunit-bridge": "^4.4|^5.4"
-            },
-            "suggest": {
-                "ext-intl": "Needed to support internationalized email addresses"
-            },
-            "type": "library",
-            "extra": {
-                "branch-alias": {
-                    "dev-master": "6.2-dev"
-                }
-            },
-            "autoload": {
-                "files": [
-                    "lib/swift_required.php"
-                ]
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Chris Corbyn"
-                },
-                {
-                    "name": "Fabien Potencier",
-                    "email": "fabien@symfony.com"
-                }
-            ],
-            "description": "Swiftmailer, free feature-rich PHP mailer",
-            "homepage": "https://swiftmailer.symfony.com",
-            "keywords": [
-                "email",
-                "mail",
-                "mailer"
-            ],
-            "support": {
-                "issues": "https://github.com/swiftmailer/swiftmailer/issues",
-                "source": "https://github.com/swiftmailer/swiftmailer/tree/v6.3.0"
-            },
-            "funding": [
-                {
-                    "url": "https://github.com/fabpot",
-                    "type": "github"
-                },
-                {
-                    "url": "https://tidelift.com/funding/github/packagist/swiftmailer/swiftmailer",
-                    "type": "tidelift"
-                }
-            ],
-            "abandoned": "symfony/mailer",
-            "time": "2021-10-18T15:26:12+00:00"
-        },
         {
             "name": "symfony/console",
             "version": "v5.4.28",
@@ -4148,6 +4072,166 @@
             ],
             "time": "2022-01-02T09:53:40+00:00"
         },
+        {
+            "name": "symfony/mailer",
+            "version": "v5.4.31",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/mailer.git",
+                "reference": "5ca8a7628a5ee69767047dd0f4cf4c9521c999b8"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/mailer/zipball/5ca8a7628a5ee69767047dd0f4cf4c9521c999b8",
+                "reference": "5ca8a7628a5ee69767047dd0f4cf4c9521c999b8",
+                "shasum": ""
+            },
+            "require": {
+                "egulias/email-validator": "^2.1.10|^3|^4",
+                "php": ">=7.2.5",
+                "psr/event-dispatcher": "^1",
+                "psr/log": "^1|^2|^3",
+                "symfony/deprecation-contracts": "^2.1|^3",
+                "symfony/event-dispatcher": "^4.4|^5.0|^6.0",
+                "symfony/mime": "^5.2.6|^6.0",
+                "symfony/polyfill-php80": "^1.16",
+                "symfony/service-contracts": "^1.1|^2|^3"
+            },
+            "conflict": {
+                "symfony/http-kernel": "<4.4"
+            },
+            "require-dev": {
+                "symfony/http-client": "^4.4|^5.0|^6.0",
+                "symfony/messenger": "^4.4|^5.0|^6.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Mailer\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Helps sending emails",
+            "homepage": "https://symfony.com",
+            "support": {
+                "source": "https://github.com/symfony/mailer/tree/v5.4.31"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2023-11-03T16:16:43+00:00"
+        },
+        {
+            "name": "symfony/mime",
+            "version": "v5.4.26",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/mime.git",
+                "reference": "2ea06dfeee20000a319d8407cea1d47533d5a9d2"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/mime/zipball/2ea06dfeee20000a319d8407cea1d47533d5a9d2",
+                "reference": "2ea06dfeee20000a319d8407cea1d47533d5a9d2",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.2.5",
+                "symfony/deprecation-contracts": "^2.1|^3",
+                "symfony/polyfill-intl-idn": "^1.10",
+                "symfony/polyfill-mbstring": "^1.0",
+                "symfony/polyfill-php80": "^1.16"
+            },
+            "conflict": {
+                "egulias/email-validator": "~3.0.0",
+                "phpdocumentor/reflection-docblock": "<3.2.2",
+                "phpdocumentor/type-resolver": "<1.4.0",
+                "symfony/mailer": "<4.4",
+                "symfony/serializer": "<5.4.26|>=6,<6.2.13|>=6.3,<6.3.2"
+            },
+            "require-dev": {
+                "egulias/email-validator": "^2.1.10|^3.1|^4",
+                "phpdocumentor/reflection-docblock": "^3.0|^4.0|^5.0",
+                "symfony/dependency-injection": "^4.4|^5.0|^6.0",
+                "symfony/property-access": "^4.4|^5.1|^6.0",
+                "symfony/property-info": "^4.4|^5.1|^6.0",
+                "symfony/serializer": "^5.4.26|~6.2.13|^6.3.2"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Mime\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Allows manipulating MIME messages",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "mime",
+                "mime-type"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/mime/tree/v5.4.26"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2023-07-27T06:29:31+00:00"
+        },
         {
             "name": "symfony/polyfill-php80",
             "version": "v1.28.0",
@@ -7231,5 +7315,5 @@
     "platform-overrides": {
         "php": "7.4"
     },
-    "plugin-api-version": "2.3.0"
+    "plugin-api-version": "2.6.0"
 }
diff --git a/composer.phar b/composer.phar
new file mode 100755
index 000000000000..553efcce527c
Binary files /dev/null and b/composer.phar differ
diff --git a/config/config.sample.php b/config/config.sample.php
index 0e6480cbf059..5d388f3a96e7 100644
--- a/config/config.sample.php
+++ b/config/config.sample.php
@@ -445,7 +445,7 @@
 
 /**
  * Define the SMTP security style
- * Depends on `mail_smtpmode`. Specify when you are using `ssl` or `tls`.
+ * Depends on `mail_smtpmode`. Specify when you are using `ssl` or not.
  * Leave empty for no encryption.
  */
 'mail_smtpsecure' => '',
@@ -456,13 +456,6 @@
  */
 'mail_smtpauth' => false,
 
-/**
- * Define the SMTP authentication type
- * Depends on `mail_smtpmode`. If SMTP authentication is required,
- * choose the authentication type as `LOGIN` (default) or `PLAIN`.
- */
-'mail_smtpauthtype' => 'LOGIN',
-
 /**
  * Define the SMTP authentication username
  * Depends on `mail_smtpauth`. Specify the username for authenticating to the SMTP server.
diff --git a/lib/private/Mail/Logger.php b/lib/private/Mail/Logger.php
new file mode 100644
index 000000000000..17b51e36a39b
--- /dev/null
+++ b/lib/private/Mail/Logger.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace OC\Mail;
+
+use Psr\Log\AbstractLogger;
+
+class Logger extends AbstractLogger {
+	private array $log;
+
+	public function log($level, $message, array $context = []) {
+		$this->log[] = [$level, $message, $context];
+	}
+
+	/**
+	 * @throws \JsonException
+	 */
+	public function toJSON(): string {
+		return json_encode($this->log, JSON_THROW_ON_ERROR);
+	}
+}
diff --git a/lib/private/Mail/Mailer.php b/lib/private/Mail/Mailer.php
index 62b33d89f22d..8a5f3eed175c 100644
--- a/lib/private/Mail/Mailer.php
+++ b/lib/private/Mail/Mailer.php
@@ -23,9 +23,17 @@
 
 use Egulias\EmailValidator\EmailValidator;
 use Egulias\EmailValidator\Validation\RFCValidation;
+use OC_Defaults;
 use OCP\IConfig;
 use OCP\Mail\IMailer;
 use OCP\ILogger;
+use Psr\Log\LoggerInterface;
+use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
+use Symfony\Component\Mailer\Transport\SendmailTransport;
+use Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport;
+use Symfony\Component\Mailer\Transport\Smtp\Stream\SocketStream;
+use Symfony\Component\Mailer\Transport\TransportInterface;
+use Symfony\Component\Mime\Email;
 
 /**
  * Class Mailer provides some basic functions to create a mail message that can be used in combination with
@@ -46,24 +54,15 @@
  * @package OC\Mail
  */
 class Mailer implements IMailer {
-	/** @var \Swift_SmtpTransport|\Swift_SendmailTransport Cached transport */
-	private $instance = null;
-	/** @var IConfig */
-	private $config;
-	/** @var ILogger */
-	private $logger;
-	/** @var \OC_Defaults */
-	private $defaults;
+	private ?TransportInterface $instance = null;
+	private IConfig $config;
+	private ILogger $logger;
+	private OC_Defaults $defaults;
 
-	/**
-	 * @param IConfig $config
-	 * @param ILogger $logger
-	 * @param \OC_Defaults $defaults
-	 */
 	public function __construct(
 		IConfig $config,
 		ILogger $logger,
-		\OC_Defaults $defaults
+		OC_Defaults $defaults
 	) {
 		$this->config = $config;
 		$this->logger = $logger;
@@ -72,11 +71,9 @@ public function __construct(
 
 	/**
 	 * Creates a new message object that can be passed to send()
-	 *
-	 * @return Message
 	 */
-	public function createMessage() {
-		return new Message(new \Swift_Message());
+	public function createMessage(): Message {
+		return new Message(new Email());
 	}
 
 	/**
@@ -89,18 +86,34 @@ public function createMessage() {
 	 * @throws \Exception In case it was not possible to send the message. (for example if an invalid mail address
 	 * has been supplied.)
 	 */
-	public function send(Message $message) {
-		$debugMode = $this->config->getSystemValue('mail_smtpdebug', false);
-
+	public function send(Message $message): array {
 		if (!\is_array($message->getFrom()) || \count($message->getFrom()) === 0) {
 			$message->setFrom([\OCP\Util::getDefaultEmailAddress($this->defaults->getName())]);
 		}
 
-		$failedRecipients = [];
-
-		$mailer = $this->getInstance();
-
-		$mailer->send($message->getSwiftMessage(), $failedRecipients);
+		$debugMode = $this->config->getSystemValue('mail_smtpdebug', false);
+		$logger = $debugMode ? new Logger() : null;
+
+		try {
+			$this->getInstance($logger ?? null)->send($message->getMessage());
+		} catch (TransportExceptionInterface $e) {
+			# in case of exception it is expected that none of the mails has been sent
+			$failedRecipients = [];
+
+			$recipients = array_merge($message->getTo(), $message->getCc(), $message->getBcc());
+			array_walk($recipients, static function ($value, $key) use (&$failedRecipients) {
+				if (is_numeric($key)) {
+					$failedRecipients[] = $value;
+				} else {
+					$failedRecipients[] = $key;
+				}
+			});
+
+			$this->logger->logException($e, ['failed-recipients' => $recipients]);
+
+			# list of failed recipients is not added by intention to not accidentally disclose private data
+			throw new \RuntimeException("Failed to deliver email", 0, $e);
+		}
 
 		$allRecipients = [];
 		if (!empty($message->getTo())) {
@@ -119,10 +132,11 @@ public function send(Message $message) {
 			'app' => 'core',
 			'from' => \json_encode($message->getFrom()),
 			'recipients' => \json_encode($allRecipients),
-			'subject' => $message->getSubject()
+			'subject' => $message->getSubject(),
+			'mail_log' => ($logger !== null) ? $logger->toJSON() : null,
 		]);
 
-		return $failedRecipients;
+		return [];
 	}
 
 	/**
@@ -131,9 +145,9 @@ public function send(Message $message) {
 	 * @param string $email Email address to be validated
 	 * @return bool True if the mail address is valid, false otherwise
 	 */
-	public function validateMailAddress($email) {
-		$validator = new EmailValidator();
-		return $validator->isValid($this->convertEmail($email), new RFCValidation());
+	public function validateMailAddress(string $email): bool {
+		return (new EmailValidator())
+			->isValid($this->convertEmail($email), new RFCValidation());
 	}
 
 	/**
@@ -144,12 +158,12 @@ public function validateMailAddress($email) {
 	 * @param string $email
 	 * @return string Converted mail address if `idn_to_ascii` exists
 	 */
-	protected function convertEmail($email) {
+	protected function convertEmail(string $email): string {
 		if (!\function_exists('idn_to_ascii') || \strpos($email, '@') === false) {
 			return $email;
 		}
 
-		list($name, $domain) = \explode('@', $email, 2);
+		[$name, $domain] = \explode('@', $email, 2);
 		if (\defined('INTL_IDNA_VARIANT_UTS46')) {
 			$domain = \idn_to_ascii($domain, 0, INTL_IDNA_VARIANT_UTS46);
 		} else {
@@ -158,80 +172,50 @@ protected function convertEmail($email) {
 		return $name.'@'.$domain;
 	}
 
-	/**
-	 * Returns whatever transport is configured within the config
-	 *
-	 * @return \Swift_SmtpTransport|\Swift_SendmailTransport
-	 */
-	protected function getInstance() {
+	protected function getInstance(?LoggerInterface $logger = null): TransportInterface {
 		if ($this->instance !== null) {
 			return $this->instance;
 		}
 
 		$mailMode = $this->config->getSystemValue('mail_smtpmode', 'php');
 		if ($mailMode === 'smtp') {
-			$instance = $this->getSmtpInstance();
+			$transport = $this->getSmtpInstance($logger ?? null);
 		} else {
-			// FIXME: Move into the return statement but requires proper testing
-			//       for SMTP and mail as well. Thus not really doable for a
-			//       minor release.
-			$instance = new \Swift_Mailer($this->getSendMailInstance());
-		}
-
-		// Register plugins
-
-		// Enable logger if debug mode is enabled
-		if ($this->config->getSystemValue('mail_smtpdebug', false)) {
-			$mailLogger = new \Swift_Plugins_Loggers_ArrayLogger();
-			$instance->registerPlugin(new \Swift_Plugins_LoggerPlugin($mailLogger));
+			$transport = $this->getSendMailInstance($logger ?? null);
 		}
 
-		// Enable antiflood on smtp connection (defaults to 100 mails before reconnect)
-		$instance->registerPlugin(new \Swift_Plugins_AntiFloodPlugin());
-
-		$this->instance = $instance;
+		$this->instance = $transport;
 
 		return $this->instance;
 	}
 
-	/**
-	 * Returns the SMTP transport
-	 *
-	 * @return \Swift_SmtpTransport
-	 */
-	protected function getSmtpInstance() {
-		$transport = new \Swift_SmtpTransport();
-		$transport->setTimeout($this->config->getSystemValue('mail_smtptimeout', 10));
-		$transport->setHost($this->config->getSystemValue('mail_smtphost', '127.0.0.1'));
-		$transport->setPort($this->config->getSystemValue('mail_smtpport', 25));
+	protected function getSmtpInstance(?LoggerInterface $logger): EsmtpTransport {
+		$timeout = $this->config->getSystemValue('mail_smtptimeout', 10);
+		$host = $this->config->getSystemValue('mail_smtphost', '127.0.0.1');
+		$port = $this->config->getSystemValue('mail_smtpport', 25);
+		$smtpSecurity = $this->config->getSystemValue('mail_smtpsecure', '');
+		$tls = $smtpSecurity === 'ssl' ? true : null;
+		$transport = new EsmtpTransport($host, $port, $tls, null, $logger);
 		if ($this->config->getSystemValue('mail_smtpauth', false)) {
 			$transport->setUsername($this->config->getSystemValue('mail_smtpname', ''));
 			$transport->setPassword($this->config->getSystemValue('mail_smtppassword', ''));
-			$transport->setAuthMode($this->config->getSystemValue('mail_smtpauthtype', 'LOGIN'));
 		}
-		$smtpSecurity = $this->config->getSystemValue('mail_smtpsecure', '');
-		if (!empty($smtpSecurity)) {
-			$transport->setEncryption($smtpSecurity);
+		$stream = $transport->getStream();
+		if ($stream instanceof SocketStream) {
+			$stream->setTimeout($timeout);
 		}
-		$transport->start();
+
 		return $transport;
 	}
 
-	/**
-	 * Returns the sendmail transport
-	 *
-	 * @return \Swift_SendmailTransport
-	 */
-	protected function getSendMailInstance() {
-		switch ($this->config->getSystemValue('mail_smtpmode', 'sendmail')) {
-			case 'qmail':
-				$binaryPath = '/var/qmail/bin/sendmail';
-				break;
-			default:
-				$binaryPath = '/usr/sbin/sendmail';
-				break;
+	protected function getSendMailInstance(?LoggerInterface $logger = null): SendmailTransport {
+		$i = $this->config->getSystemValue('mail_smtpmode', 'sendmail');
+		if ($i === 'qmail') {
+			$binaryPath = '/var/qmail/bin/sendmail';
+		} else {
+			$binaryPath = '/usr/sbin/sendmail';
 		}
 
-		return new \Swift_SendmailTransport($binaryPath . ' -bs');
+		return new SendmailTransport($binaryPath . ' -bs', null, $logger);
 	}
 }
diff --git a/lib/private/Mail/Message.php b/lib/private/Mail/Message.php
index 12633ff76ad6..88ce719abf07 100644
--- a/lib/private/Mail/Message.php
+++ b/lib/private/Mail/Message.php
@@ -22,55 +22,38 @@
 
 namespace OC\Mail;
 
-use Swift_Message;
+use Symfony\Component\Mime\Address;
+use Symfony\Component\Mime\Email;
 
 /**
- * Class Message provides a wrapper around SwiftMail
+ * Class Message provides a wrapper around Symfony\Component\Mime\Email
  *
  * @package OC\Mail
  */
 class Message {
-	/** @var Swift_Message */
-	private $swiftMessage;
+	private Email $message;
+	private array $from = [];
+	private array $replyTo = [];
+	private array $to = [];
+	private array $cc = [];
+	private array $bcc = [];
 
-	/**
-	 * @param Swift_Message $swiftMessage
-	 */
-	public function __construct(Swift_Message $swiftMessage) {
-		$this->swiftMessage = $swiftMessage;
+	public function __construct(Email $swiftMessage) {
+		$this->message = $swiftMessage;
 	}
 
 	/**
-	 * SwiftMailer does currently not work with IDN domains, this function therefore converts the domains
-	 * FIXME: Remove this once SwiftMailer supports IDN
-	 *
 	 * @param array $addresses Array of mail addresses, key will get converted
-	 * @return array Converted addresses if `idn_to_ascii` exists
+	 * @return Address[] Converted addresses if `idn_to_ascii` exists
 	 */
-	protected function convertAddresses($addresses) {
-		if (!\function_exists('idn_to_ascii')) {
-			return $addresses;
-		}
-
+	protected function convertAddresses(array $addresses): array {
 		$convertedAddresses = [];
 
 		foreach ($addresses as $email => $readableName) {
-			if (!\is_numeric($email)) {
-				list($name, $domain) = \explode('@', $email, 2);
-				if (\defined('INTL_IDNA_VARIANT_UTS46')) {
-					$domain = \idn_to_ascii($domain, 0, INTL_IDNA_VARIANT_UTS46);
-				} else {
-					$domain = \idn_to_ascii($domain);
-				}
-				$convertedAddresses[$name.'@'.$domain] = $readableName;
+			if (\is_numeric($email)) {
+				$convertedAddresses[] = new Address($readableName);
 			} else {
-				list($name, $domain) = \explode('@', $readableName, 2);
-				if (\defined('INTL_IDNA_VARIANT_UTS46')) {
-					$domain = \idn_to_ascii($domain, 0, INTL_IDNA_VARIANT_UTS46);
-				} else {
-					$domain = \idn_to_ascii($domain);
-				}
-				$convertedAddresses[$email] = $name.'@'.$domain;
+				$convertedAddresses[] = new Address($email, $readableName ?? '');
 			}
 		}
 
@@ -83,12 +66,11 @@ protected function convertAddresses($addresses) {
 	 * If no "From" address is used \OC\Mail\Mailer will use mail_from_address and mail_domain from config.php
 	 *
 	 * @param array $addresses Example: array('sender@domain.org', 'other@domain.org' => 'A name')
-	 * @return $this
 	 */
-	public function setFrom(array $addresses) {
-		$addresses = $this->convertAddresses($addresses);
+	public function setFrom(array $addresses): Message {
+		$this->message->from(...$this->convertAddresses($addresses));
 
-		$this->swiftMessage->setFrom($addresses);
+		$this->from = $addresses;
 		return $this;
 	}
 
@@ -97,42 +79,36 @@ public function setFrom(array $addresses) {
 	 *
 	 * @return array
 	 */
-	public function getFrom() {
-		return $this->swiftMessage->getFrom();
+	public function getFrom(): array {
+		return $this->from;
 	}
 
 	/**
 	 * Set the Reply-To address of this message
-	 *
-	 * @param array $addresses
-	 * @return $this
 	 */
-	public function setReplyTo(array $addresses) {
-		$addresses = $this->convertAddresses($addresses);
+	public function setReplyTo(array $addresses): Message {
+		$this->message->replyTo(...$this->convertAddresses($addresses));
 
-		$this->swiftMessage->setReplyTo($addresses);
+		$this->replyTo = $addresses;
 		return $this;
 	}
 
 	/**
 	 * Returns the Reply-To address of this message
-	 *
-	 * @return array
 	 */
-	public function getReplyTo() {
-		return $this->swiftMessage->getReplyTo();
+	public function getReplyTo(): array {
+		return $this->replyTo;
 	}
 
 	/**
-	 * Set the to addresses of this message.
+	 * Set the to-addresses of this message.
 	 *
 	 * @param array $recipients Example: array('recipient@domain.org', 'other@domain.org' => 'A name')
-	 * @return $this
 	 */
-	public function setTo(array $recipients) {
-		$recipients = $this->convertAddresses($recipients);
+	public function setTo(array $recipients): Message {
+		$this->message->to(...$this->convertAddresses($recipients));
 
-		$this->swiftMessage->setTo($recipients);
+		$this->to = $recipients;
 		return $this;
 	}
 
@@ -141,82 +117,68 @@ public function setTo(array $recipients) {
 	 *
 	 * @return array
 	 */
-	public function getTo() {
-		return $this->swiftMessage->getTo();
+	public function getTo(): array {
+		return $this->to;
 	}
 
 	/**
 	 * Set the CC recipients of this message.
 	 *
 	 * @param array $recipients Example: array('recipient@domain.org', 'other@domain.org' => 'A name')
-	 * @return $this
 	 */
-	public function setCc(array $recipients) {
-		$recipients = $this->convertAddresses($recipients);
+	public function setCc(array $recipients): Message {
+		$this->message->cc(...$this->convertAddresses($recipients));
 
-		$this->swiftMessage->setCc($recipients);
+		$this->cc = $recipients;
 		return $this;
 	}
 
 	/**
 	 * Get the cc address of this message.
-	 *
-	 * @return array
 	 */
-	public function getCc() {
-		return $this->swiftMessage->getCc();
+	public function getCc(): array {
+		return $this->cc;
 	}
 
 	/**
 	 * Set the BCC recipients of this message.
 	 *
 	 * @param array $recipients Example: array('recipient@domain.org', 'other@domain.org' => 'A name')
-	 * @return $this
 	 */
-	public function setBcc(array $recipients) {
-		$recipients = $this->convertAddresses($recipients);
+	public function setBcc(array $recipients): Message {
+		$this->message->bcc(...$this->convertAddresses($recipients));
 
-		$this->swiftMessage->setBcc($recipients);
+		$this->bcc = $recipients;
 		return $this;
 	}
 
 	/**
 	 * Get the Bcc address of this message.
-	 *
-	 * @return array
 	 */
-	public function getBcc() {
-		return $this->swiftMessage->getBcc();
+	public function getBcc(): array {
+		return $this->bcc;
 	}
 
 	/**
 	 * Set the subject of this message.
-	 *
-	 * @param $subject
-	 * @return $this
 	 */
-	public function setSubject($subject) {
-		$this->swiftMessage->setSubject($subject);
+	public function setSubject(string $subject): Message {
+		$this->message->subject($subject);
 		return $this;
 	}
 
 	/**
-	 * Get the from subject of this message.
-	 *
-	 * @return string
+	 * Get the subject of this message.
 	 */
-	public function getSubject() {
-		return $this->swiftMessage->getSubject();
+	public function getSubject(): string {
+		return $this->message->getSubject();
 	}
 
 	/**
 	 * Set the plain-text body of this message.
-	 *
-	 * @param string $body
-	 * @return $this
 	 */
-	public function setPlainBody($body) {
-		$this->swiftMessage->setBody($body);
+	public function setPlainBody(string $body): Message {
+		$this->message->text($body);
 		return $this;
 	}
 
@@ -225,8 +187,8 @@ public function setPlainBody($body) {
 	 *
 	 * @return string
 	 */
-	public function getPlainBody() {
-		return $this->swiftMessage->getBody();
+	public function getPlainBody(): string {
+		return $this->message->getTextBody() ?? '';
 	}
 
 	/**
@@ -235,26 +197,27 @@ public function getPlainBody() {
 	 * @param string $body
 	 * @return $this
 	 */
-	public function setHtmlBody($body) {
-		$this->swiftMessage->addPart($body, 'text/html');
+	public function setHtmlBody(string $body): Message {
+		$this->message->html($body);
 		return $this;
 	}
 
-	/**
-	 * Get's the underlying SwiftMessage
-	 * @return Swift_Message
-	 */
-	public function getSwiftMessage() {
-		return $this->swiftMessage;
+	public function getMessage(): Email {
+		return $this->message;
 	}
 
-	/**
-	 * @param string $body
-	 * @param string $contentType
-	 * @return $this
-	 */
-	public function setBody($body, $contentType) {
-		$this->swiftMessage->setBody($body, $contentType);
+	public function setBody(string $body, string $contentType): Message {
+		if ($contentType === 'text/html') {
+			$this->message->html($body);
+		} else {
+			$this->message->text($body);
+		}
+
+		return $this;
+	}
+
+	public function attach($body, string $name = null, string $contentType = null): self {
+		$this->message->attach($body, $name, $contentType);
 		return $this;
 	}
 }
diff --git a/lib/public/Mail/IMailer.php b/lib/public/Mail/IMailer.php
index 333e961d071c..070dc42737ea 100644
--- a/lib/public/Mail/IMailer.php
+++ b/lib/public/Mail/IMailer.php
@@ -51,7 +51,7 @@ interface IMailer {
 	 * @return Message
 	 * @since 8.1.0
 	 */
-	public function createMessage();
+	public function createMessage(): Message;
 
 	/**
 	 * Send the specified message. Also sets the from address to the value defined in config.php
@@ -64,7 +64,7 @@ public function createMessage();
 	 * has been supplied.)
 	 * @since 8.1.0
 	 */
-	public function send(Message $message);
+	public function send(Message $message): array;
 
 	/**
 	 * Checks if an e-mail address is valid
@@ -73,5 +73,5 @@ public function send(Message $message);
 	 * @return bool True if the mail address is valid, false otherwise
 	 * @since 8.1.0
 	 */
-	public function validateMailAddress($email);
+	public function validateMailAddress(string $email): bool;
 }
diff --git a/settings/Controller/MailSettingsController.php b/settings/Controller/MailSettingsController.php
index 9e6e3287e1d4..9f89b3e311d2 100644
--- a/settings/Controller/MailSettingsController.php
+++ b/settings/Controller/MailSettingsController.php
@@ -85,7 +85,6 @@ public function __construct(
 	 * @param string $mail_smtpmode
 	 * @param string $mail_smtpsecure
 	 * @param string $mail_smtphost
-	 * @param string $mail_smtpauthtype
 	 * @param int $mail_smtpauth
 	 * @param string $mail_smtpport
 	 * @return array
@@ -96,7 +95,6 @@ public function setMailSettings(
 		$mail_smtpmode,
 		$mail_smtpsecure,
 		$mail_smtphost,
-		$mail_smtpauthtype,
 		$mail_smtpauth,
 		$mail_smtpport
 	) {
@@ -162,36 +160,35 @@ public function sendTestMail() {
 			$email = $this->userSession->getUser()->getEMailAddress();
 		}
 
-		if (!empty($email)) {
-			try {
-				$message = $this->mailer->createMessage();
-				$message->setTo([$email => $this->userSession->getUser()->getDisplayName()]);
-				$message->setFrom([$this->defaultMailAddress]);
-				$message->setSubject($this->l10n->t('test email settings'));
-				$message->setPlainBody('If you received this email, the settings seem to be correct.');
-				$this->mailer->send($message);
-			} catch (\Exception $e) {
-				return [
-					'data' => [
-						'message' => (string) $this->l10n->t('A problem occurred while sending the email. Please revise your settings. (Error: %s)', [$e->getMessage()]),
-					],
-					'status' => 'error',
-				];
-			}
+		if (empty($email)) {
+			return ['data' =>
+				['message' =>
+					(string) $this->l10n->t('You need to set your user email before being able to send test emails.'),
+				],
+				'status' => 'error'
+			];
+		}
 
+		try {
+			$message = $this->mailer->createMessage();
+			$message->setTo([$email => $this->userSession->getUser()->getDisplayName()]);
+			$message->setFrom([$this->defaultMailAddress]);
+			$message->setSubject($this->l10n->t('test email settings'));
+			$message->setPlainBody('If you received this email, the settings seem to be correct.');
+			$this->mailer->send($message);
 			return ['data' =>
 				['message' =>
 					(string) $this->l10n->t('Email sent')
 				],
 				'status' => 'success'
 			];
+		} catch (\Exception $e) {
+			return [
+				'data' => [
+					'message' => (string) $this->l10n->t('A problem occurred while sending the email. Please revise your settings. (Error: %s)', [$e->getMessage()]),
+				],
+				'status' => 'error',
+			];
 		}
-
-		return ['data' =>
-			['message' =>
-				(string) $this->l10n->t('You need to set your user email before being able to send test emails.'),
-			],
-			'status' => 'error'
-		];
 	}
 }
diff --git a/settings/Panels/Admin/Mail.php b/settings/Panels/Admin/Mail.php
index 4a86cb8b34fc..0c75b63a9f61 100644
--- a/settings/Panels/Admin/Mail.php
+++ b/settings/Panels/Admin/Mail.php
@@ -61,7 +61,6 @@ public function getPanel() {
 		$template->assign('mail_smtpsecure', $this->config->getSystemValue("mail_smtpsecure", ''));
 		$template->assign('mail_smtphost', $this->config->getSystemValue("mail_smtphost", ''));
 		$template->assign('mail_smtpport', $this->config->getSystemValue("mail_smtpport", ''));
-		$template->assign('mail_smtpauthtype', $this->config->getSystemValue("mail_smtpauthtype", ''));
 		$template->assign('mail_smtpauth', $this->config->getSystemValue("mail_smtpauth", false));
 		$template->assign('mail_smtpname', $this->config->getSystemValue("mail_smtpname", ''));
 		$template->assign('mail_user_email', $this->userSession->getUser()->getEMailAddress());
diff --git a/settings/templates/panels/admin/mail.php b/settings/templates/panels/admin/mail.php
index 8604fb4d9a25..45394de5ffc9 100644
--- a/settings/templates/panels/admin/mail.php
+++ b/settings/templates/panels/admin/mail.php
@@ -1,15 +1,8 @@
 <?php
 script('settings', 'panels/mail');
-$mail_smtpauthtype = [
-	''	=> $l->t('None'),
-	'LOGIN'	=> $l->t('Login'),
-	'PLAIN'	=> $l->t('Plain'),
-	'NTLM'	=> $l->t('NT LAN Manager'),
-];
 $mail_smtpsecure = [
 	''		=> $l->t('None'),
 	'ssl'	=> $l->t('SSL/TLS'),
-	'tls'	=> $l->t('STARTTLS'),
 ];
 $mail_smtpmode = [
 	'php',
@@ -80,17 +73,6 @@
 			<p id="setting_smtpauth" <?php if ($_['mail_smtpmode'] != 'smtp') {
 				print_unescaped(' class="hidden"');
 			} ?>>
-				<label for="mail_smtpauthtype"><?php p($l->t('Authentication method')); ?></label>
-				<select name='mail_smtpauthtype' id='mail_smtpauthtype'>
-					<?php foreach ($mail_smtpauthtype as $authtype => $name):
-						$selected = '';
-						if ($authtype == $_['mail_smtpauthtype']):
-							$selected = 'selected="selected"';
-						endif; ?>
-						<option value='<?php p($authtype)?>' <?php p($selected) ?>><?php p($name) ?></option>
-					<?php endforeach;?>
-				</select>
-
 				<input type="checkbox" name="mail_smtpauth" id="mail_smtpauth" class="checkbox" value="1"
 					   <?php if ($_['mail_smtpauth']) {
 					   	print_unescaped('checked="checked"');
diff --git a/tests/Settings/Controller/MailSettingsControllerTest.php b/tests/Settings/Controller/MailSettingsControllerTest.php
index c37206aa97fd..98fd00d75801 100644
--- a/tests/Settings/Controller/MailSettingsControllerTest.php
+++ b/tests/Settings/Controller/MailSettingsControllerTest.php
@@ -11,46 +11,52 @@
 namespace Tests\Settings\Controller;
 
 use OC\Settings\Application;
+use OCP\AppFramework\IAppContainer;
+use PHPUnit\Framework\MockObject\MockObject;
+use Test\TestCase;
+use OC\User\User;
+use OCP\IConfig;
+use OCP\IL10N;
+use OC\User\Session;
+use OC\Mail\Mailer;
 
 /**
  * @package Tests\Settings\Controller
  */
-class MailSettingsControllerTest extends \Test\TestCase {
-	private $container;
+class MailSettingsControllerTest extends TestCase {
+	private IAppContainer $container;
 
 	protected function setUp(): void {
 		parent::setUp();
 
 		$app = new Application();
 		$this->container = $app->getContainer();
-		$this->container['Config'] = $this->getMockBuilder('\OCP\IConfig')
+		$this->container['Config'] = $this->getMockBuilder(IConfig::class)
 			->disableOriginalConstructor()->getMock();
-		$this->container['L10N'] = $this->getMockBuilder('\OCP\IL10N')
+		$this->container['L10N'] = $this->getMockBuilder(IL10N::class)
 			->disableOriginalConstructor()->getMock();
 		$this->container['AppName'] = 'settings';
-		$this->container['UserSession'] = $this->getMockBuilder('\OC\User\Session')
+		$this->container['UserSession'] = $this->getMockBuilder(Session::class)
 			->disableOriginalConstructor()->getMock();
-		$this->container['MailMessage'] = $this->getMockBuilder('\OCP\Mail\IMessage')
-			->disableOriginalConstructor()->getMock();
-		$this->container['Mailer'] = $this->getMockBuilder('\OC\Mail\Mailer')
+		$this->container['Mailer'] = $this->getMockBuilder(Mailer::class)
 			->setMethods(['send', 'validateMailAddress'])
 			->disableOriginalConstructor()->getMock();
-		$this->container['Defaults'] = $this->getMockBuilder('\OC_Defaults')
+		$this->container['Defaults'] = $this->getMockBuilder(\OC_Defaults::class)
 			->disableOriginalConstructor()->getMock();
 		$this->container['DefaultMailAddress'] = 'no-reply@owncloud.com';
 	}
 
-	public function testSetInvalidMail() {
+	public function testSetInvalidMail(): void {
 		$this->container['L10N']
 			->expects($this->exactly(2))
 			->method('t')
-			->will($this->returnValue('Invalid email address'));
+			->willReturn('Invalid email address');
 
 		$this->container['Mailer']
 			->expects($this->exactly(2))
 			->method('validateMailAddress')
 			->with('@@owncloud.com')
-			->will($this->returnValue(false));
+			->willReturn(false);
 
 		// With authentication
 		$response = $this->container['MailSettingsController']->setMailSettings(
@@ -77,54 +83,26 @@ public function testSetInvalidMail() {
 			0,
 			'25'
 		);
-		$expectedResponse = ['data' => ['message' =>'Invalid email address'], 'status' => 'error'];
+
 		$this->assertSame($expectedResponse, $response);
 	}
 
-	public function testSetMailSettings() {
+	public function testSetMailSettings(): void {
 		$this->container['L10N']
 			->expects($this->exactly(2))
 			->method('t')
-			->will($this->returnValue('Saved'));
-
-		/**
-		 * FIXME: Use the following block once Jenkins uses PHPUnit >= 4.1
-		 */
-		/*
-		$this->container['Config']
-			->expects($this->exactly(15))
-			->method('setSystemValue')
-			->withConsecutive(
-				array($this->equalTo('mail_domain'), $this->equalTo('owncloud.com')),
-				array($this->equalTo('mail_from_address'), $this->equalTo('demo')),
-				array($this->equalTo('mail_smtpmode'), $this->equalTo('smtp')),
-				array($this->equalTo('mail_smtpsecure'), $this->equalTo('ssl')),
-				array($this->equalTo('mail_smtphost'), $this->equalTo('mx.owncloud.com')),
-				array($this->equalTo('mail_smtpauthtype'), $this->equalTo('NTLM')),
-				array($this->equalTo('mail_smtpauth'), $this->equalTo(1)),
-				array($this->equalTo('mail_smtpport'), $this->equalTo('25')),
-				array($this->equalTo('mail_domain'), $this->equalTo('owncloud.com')),
-				array($this->equalTo('mail_from_address'), $this->equalTo('demo@owncloud.com')),
-				array($this->equalTo('mail_smtpmode'), $this->equalTo('smtp')),
-				array($this->equalTo('mail_smtpsecure'), $this->equalTo('ssl')),
-				array($this->equalTo('mail_smtphost'), $this->equalTo('mx.owncloud.com')),
-				array($this->equalTo('mail_smtpauthtype'), $this->equalTo('NTLM')),
-				array($this->equalTo('mail_smtpport'), $this->equalTo('25'))
-			);
-		 */
+			->willReturn('Saved');
 
 		$this->container['Mailer']
 			->expects($this->exactly(2))
 			->method('validateMailAddress')
 			->with('demo@owncloud.com')
-			->will($this->returnValue(true));
+			->willReturn(true);
 
-		/** @var \PHPUnit\Framework\MockObject\MockObject $config */
+		/** @var MockObject $config */
 		$config = $this->container['Config'];
 		$config->expects($this->exactly(2))
-			->method('setSystemValues');
-		/**
-		 * FIXME: Use the following block once Jenkins uses PHPUnit >= 4.1
+			->method('setSystemValues')
 			->withConsecutive(
 				[[
 					'mail_domain' => 'owncloud.com',
@@ -132,7 +110,6 @@ public function testSetMailSettings() {
 					'mail_smtpmode' => 'smtp',
 					'mail_smtpsecure' => 'ssl',
 					'mail_smtphost' => 'mx.owncloud.com',
-					'mail_smtpauthtype' => 'NTLM',
 					'mail_smtpauth' => 1,
 					'mail_smtpport' => '25',
 				]],
@@ -142,14 +119,12 @@ public function testSetMailSettings() {
 					'mail_smtpmode' => 'smtp',
 					'mail_smtpsecure' => 'ssl',
 					'mail_smtphost' => 'mx.owncloud.com',
-					'mail_smtpauthtype' => 'NTLM',
 					'mail_smtpauth' => null,
-					'mail_smtpport' => '25',
+					'mail_smtpport' => '587',
 					'mail_smtpname' => null,
-					'mail_smtppassword' => null,
+					'mail_smtppassword' => null
 				]]
 			);
-		 */
 
 		// With authentication
 		$response = $this->container['MailSettingsController']->setMailSettings(
@@ -158,7 +133,6 @@ public function testSetMailSettings() {
 			'smtp',
 			'ssl',
 			'mx.owncloud.com',
-			'NTLM',
 			1,
 			'25'
 		);
@@ -172,19 +146,17 @@ public function testSetMailSettings() {
 			'smtp',
 			'ssl',
 			'mx.owncloud.com',
-			'NTLM',
 			0,
-			'25'
+			'587'
 		);
-		$expectedResponse = ['data' => ['message' =>'Saved'], 'status' => 'success'];
 		$this->assertSame($expectedResponse, $response);
 	}
 
-	public function testStoreCredentials() {
+	public function testStoreCredentials(): void {
 		$this->container['L10N']
 			->expects($this->once())
 			->method('t')
-			->will($this->returnValue('Saved'));
+			->willReturn('Saved');
 
 		$this->container['Config']
 			->expects($this->once())
@@ -200,47 +172,43 @@ public function testStoreCredentials() {
 		$this->assertSame($expectedResponse, $response);
 	}
 
-	public function testSendTestMail() {
-		$user = $this->getMockBuilder('\OC\User\User')
+	public function testSendTestMail(): void {
+		$user = $this->getMockBuilder(User::class)
 			->disableOriginalConstructor()
 			->getMock();
-		$user->expects($this->any())
+		$user
 			->method('getUID')
-			->will($this->returnValue('Werner'));
-		$user->expects($this->any())
+			->willReturn('Werner');
+		$user
 			->method('getDisplayName')
-			->will($this->returnValue('Werner Brösel'));
+			->willReturn('Werner Brösel');
 
 		$this->container['L10N']
-			->expects($this->any())
 			->method('t')
-			->will(
-				$this->returnValueMap(
-					[
-						['You need to set your user email before being able to send test emails.', [],
-							'You need to set your user email before being able to send test emails.'],
-						['A problem occurred while sending the e-mail. Please revisit your settings.', [],
-							'A problem occurred while sending the e-mail. Please revisit your settings.'],
-						['Email sent', [], 'Email sent'],
-						['test email settings', [], 'test email settings'],
-						['If you received this email, the settings seem to be correct.', [],
-							'If you received this email, the settings seem to be correct.']
-					]
-				)
+			->willReturnMap(
+				[
+					['You need to set your user email before being able to send test emails.', [],
+						'You need to set your user email before being able to send test emails.'],
+					['A problem occurred while sending the e-mail. Please revisit your settings.', [],
+						'A problem occurred while sending the e-mail. Please revisit your settings.'],
+					['Email sent', [], 'Email sent'],
+					['test email settings', [], 'test email settings'],
+					['If you received this email, the settings seem to be correct.', [],
+						'If you received this email, the settings seem to be correct.']
+				]
 			);
 		$this->container['UserSession']
-			->expects($this->any())
 			->method('getUser')
-			->will($this->returnValue($user));
+			->willReturn($user);
 
 		// Ensure that it fails when no mail address has been specified
 		$response = $this->container['MailSettingsController']->sendTestMail();
 		$expectedResponse = ['data' => ['message' =>'You need to set your user email before being able to send test emails.'], 'status' => 'error'];
 		$this->assertSame($expectedResponse, $response);
 
-		$user->expects($this->any())
+		$user
 			->method('getEMailAddress')
-			->will($this->returnValue('mail@example.invalid'));
+			->willReturn('mail@example.invalid');
 		$response = $this->container['MailSettingsController']->sendTestMail();
 		$expectedResponse = ['data' => ['message' =>'Email sent'], 'status' => 'success'];
 		$this->assertSame($expectedResponse, $response);
diff --git a/tests/Settings/Controller/UsersControllerTest.php b/tests/Settings/Controller/UsersControllerTest.php
index ebe2b64b1462..0ce11dd3bc0b 100644
--- a/tests/Settings/Controller/UsersControllerTest.php
+++ b/tests/Settings/Controller/UsersControllerTest.php
@@ -3530,6 +3530,10 @@ public function testSetPassword(): void {
 			->method('send')
 			->with($message)
 			->willReturn([]);
+		$l10n->method('t')
+			->willReturnCallback(function ($text, $parameters = []) {
+				return \vsprintf($text, $parameters);
+			});
 
 		$result = $usersController->setPassword('fooBaZ1', 'foo', '123');
 		$this->assertEquals(new Http\JSONResponse(['status' => 'success']), $result);
diff --git a/tests/acceptance/features/lib/AdminGeneralSettingsPage.php b/tests/acceptance/features/lib/AdminGeneralSettingsPage.php
index 38c4f5cbf3cb..2815d420159e 100644
--- a/tests/acceptance/features/lib/AdminGeneralSettingsPage.php
+++ b/tests/acceptance/features/lib/AdminGeneralSettingsPage.php
@@ -43,7 +43,6 @@ class AdminGeneralSettingsPage extends OwncloudPage {
 	protected $encryptionTypeId = 'mail_smtpsecure';
 	protected $mailFromAddressFieldId = 'mail_from_address';
 	protected $mailDomainFieldId = 'mail_domain';
-	protected $authMethodTypeId = 'mail_smtpauthtype';
 	protected $authRequiredCheckboxXpath = '//label[@for="mail_smtpauth"]';
 	protected $authRequiredCheckboxId = 'mail_smtpauth';
 	protected $serverAddressFieldId = 'mail_smtphost';
@@ -89,8 +88,6 @@ public function setEmailServerSettings(Session $session, TableNode $emailSetting
 				$this->fillField($this->mailFromAddressFieldId, $row['value']);
 			} elseif ($row['setting'] === 'mail domain') {
 				$this->fillField($this->mailDomainFieldId, $row['value']);
-			} elseif ($row['setting'] === 'authentication method') {
-				$this->selectFieldOption($this->authMethodTypeId, $row['value']);
 			} elseif ($row['setting'] === 'authentication required') {
 				$this->checkRequiredAuthentication($row['value']);
 			} elseif ($row['setting'] === 'server address') {
diff --git a/tests/lib/Mail/MailerTest.php b/tests/lib/Mail/MailerTest.php
index fc02360b0a6b..d1b50f8ae1e3 100644
--- a/tests/lib/Mail/MailerTest.php
+++ b/tests/lib/Mail/MailerTest.php
@@ -8,19 +8,25 @@
 
 namespace Test\Mail;
 
+use Exception;
 use OC\Mail\Mailer;
 use OC_Defaults;
 use OCP\IConfig;
 use OCP\ILogger;
+use PHPUnit\Framework\MockObject\MockObject;
+use Symfony\Component\Mailer\Transport\SendmailTransport;
+use Symfony\Component\Mime\Email;
 use Test\TestCase;
 use OC\Mail\Message;
+use function array_merge;
+use function json_encode;
 
 class MailerTest extends TestCase {
-	/** @var IConfig | \PHPUnit\Framework\MockObject\MockObject */
+	/** @var IConfig | MockObject */
 	private $config;
 	/** @var OC_Defaults */
 	private $defaults;
-	/** @var ILogger | \PHPUnit\Framework\MockObject\MockObject */
+	/** @var ILogger | MockObject */
 	private $logger;
 	/** @var Mailer */
 	private $mailer;
@@ -42,11 +48,12 @@ public function testGetSendMailInstanceSendMail(): void {
 			->expects($this->once())
 			->method('getSystemValue')
 			->with('mail_smtpmode', 'sendmail')
-			->will($this->returnValue('sendmail'));
+			->willReturn('sendmail');
 
+		/** @var SendmailTransport $mailer */
 		$mailer = self::invokePrivate($this->mailer, 'getSendMailInstance');
-		$this->assertInstanceOf(\Swift_SendmailTransport::class, $mailer);
-		$this->assertEquals('/usr/sbin/sendmail -bs', $mailer->getCommand());
+		$this->assertInstanceOf(SendmailTransport::class, $mailer);
+		$this->assertEquals('/usr/sbin/sendmail -bs', self::invokePrivate($mailer, 'command'));
 	}
 
 	public function testGetSendMailInstanceSendMailQmail(): void {
@@ -54,39 +61,33 @@ public function testGetSendMailInstanceSendMailQmail(): void {
 			->expects($this->once())
 			->method('getSystemValue')
 			->with('mail_smtpmode', 'sendmail')
-			->will($this->returnValue('qmail'));
+			->willReturn('qmail');
 		$mailer = self::invokePrivate($this->mailer, 'getSendMailInstance');
-		$this->assertInstanceOf(\Swift_SendmailTransport::class, $mailer);
-		$this->assertEquals('/var/qmail/bin/sendmail -bs', $mailer->getCommand());
+		$this->assertInstanceOf(SendmailTransport::class, $mailer);
+		$this->assertEquals('/var/qmail/bin/sendmail -bs', self::invokePrivate($mailer, 'command'));
 	}
 
 	public function testGetInstanceDefault(): void {
-		$this->assertInstanceOf(\Swift_Mailer::class, self::invokePrivate($this->mailer, 'getInstance'));
+		$this->assertInstanceOf(SendmailTransport::class, self::invokePrivate($this->mailer, 'getInstance'));
 	}
 
 	public function testGetInstanceSendmail(): void {
 		$this->config
 			->method('getSystemValue')
-			->will($this->returnValue('sendmail'));
+			->willReturn('sendmail');
 
-		$this->assertInstanceOf(\Swift_Mailer::class, self::invokePrivate($this->mailer, 'getInstance'));
+		$this->assertInstanceOf(SendmailTransport::class, self::invokePrivate($this->mailer, 'getInstance'));
 	}
 
-	public function testCreateMessage(): void {
-		$this->assertInstanceOf(Message::class, $this->mailer->createMessage());
-	}
-
-	/**
-	 */
 	public function testSendInvalidMailException(): void {
-		$this->expectException(\Exception::class);
+		$this->expectException(Exception::class);
 
-		/** @var Message | \PHPUnit\Framework\MockObject\MockObject $message */
+		/** @var Message | MockObject $message */
 		$message = $this->getMockBuilder(Message::class)
 			->disableOriginalConstructor()->getMock();
 		$message->expects($this->once())
-			->method('getSwiftMessage')
-			->will($this->returnValue(new \Swift_Message()));
+			->method('getMessage')
+			->willReturn(new Email());
 
 		$this->mailer->send($message);
 	}
@@ -119,14 +120,14 @@ public function testLogEntry(): void {
 			->setMethods(['getInstance'])
 			->getMock();
 
-		$this->mailer->method('getInstance')->willReturn($this->createMock(\Swift_SendmailTransport::class));
+		$this->mailer->method('getInstance')->willReturn($this->createMock(SendmailTransport::class));
 
-		/** @var Message | \PHPUnit\Framework\MockObject\MockObject $message */
+		/** @var Message | MockObject $message */
 		$message = $this->getMockBuilder(Message::class)
 			->disableOriginalConstructor()->getMock();
 		$message->expects($this->once())
-			->method('getSwiftMessage')
-			->will($this->returnValue(new \Swift_Message()));
+			->method('getMessage')
+			->willReturn(new Email());
 
 		$from = ['from@example.org' => 'From Address'];
 		$to = ['to1@example.org' => 'To Address 1', 'to2@example.org' => 'To Address 2'];
@@ -143,9 +144,10 @@ public function testLogEntry(): void {
 			->method('debug')
 			->with('Sent mail from "{from}" to "{recipients}" with subject "{subject}"', [
 				'app' => 'core',
-				'from' => \json_encode($from),
-				'recipients' => \json_encode(\array_merge($to, $cc, $bcc)),
-				'subject' => 'Email subject'
+				'from' => json_encode($from),
+				'recipients' => json_encode(array_merge($to, $cc, $bcc)),
+				'subject' => 'Email subject',
+				'mail_log' => null
 			]);
 
 		$this->mailer->send($message);
diff --git a/tests/lib/Mail/MessageTest.php b/tests/lib/Mail/MessageTest.php
index 8fd493883ac5..cc4dbe64bc93 100644
--- a/tests/lib/Mail/MessageTest.php
+++ b/tests/lib/Mail/MessageTest.php
@@ -9,174 +9,68 @@
 namespace Test\Mail;
 
 use OC\Mail\Message;
-use Swift_Message;
+use Symfony\Component\Mime\Address;
+use Symfony\Component\Mime\Email;
 use Test\TestCase;
 
 class MessageTest extends TestCase {
-	/** @var Swift_Message */
-	private $swiftMessage;
-	/** @var Message */
-	private $message;
-
-	/**
-	 * @return array
-	 */
-	public function mailAddressProvider() {
-		return [
-			[['lukas@owncloud.com' => 'Lukas Reschke'], ['lukas@owncloud.com' => 'Lukas Reschke']],
-			[['lukas@owncloud.com' => 'Lukas Reschke', 'lukas@öwnclöüd.com', 'lukäs@owncloud.örg' => 'Lükäs Réschke'],
-				['lukas@owncloud.com' => 'Lukas Reschke', 'lukas@xn--wncld-iuae2c.com', 'lukäs@owncloud.xn--rg-eka' => 'Lükäs Réschke']],
-			[['lukas@öwnclöüd.com'], ['lukas@xn--wncld-iuae2c.com']]
-		];
-	}
+	private Email $symfonyMail;
+	private Message $message;
 
 	public function setUp(): void {
 		parent::setUp();
 
-		$this->swiftMessage = $this->getMockBuilder('\Swift_Message')
-			->disableOriginalConstructor()->getMock();
-
-		$this->message = new Message($this->swiftMessage);
-	}
-
-	/**
-	 * @requires function idn_to_ascii
-	 * @dataProvider mailAddressProvider
-	 *
-	 * @param string $unconverted
-	 * @param string $expected
-	 */
-	public function testConvertAddresses($unconverted, $expected) {
-		$this->assertSame($expected, self::invokePrivate($this->message, 'convertAddresses', [$unconverted]));
+		$this->symfonyMail = new Email();
+		$this->message = new Message($this->symfonyMail);
 	}
 
-	public function testSetFrom() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('setFrom')
-			->with(['lukas@owncloud.com']);
+	public function testFrom(): void {
 		$this->message->setFrom(['lukas@owncloud.com']);
-	}
-
-	public function testGetFrom() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('getFrom')
-			->will($this->returnValue(['lukas@owncloud.com']));
-
 		$this->assertSame(['lukas@owncloud.com'], $this->message->getFrom());
+		$this->assertEquals([new Address('lukas@owncloud.com')], $this->symfonyMail->getFrom());
 	}
 
-	public function testSetReplyTo() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('setReplyTo')
-			->with(['lukas@owncloud.com']);
-		$this->message->setReplyTo(['lukas@owncloud.com']);
-	}
-
-	public function testGetReplyTo() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('getReplyTo')
-			->will($this->returnValue(['lukas@owncloud.com']));
-
-		$this->assertSame(['lukas@owncloud.com'], $this->message->getReplyTo());
-	}
-
-	public function testSetTo() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('setTo')
-			->with(['lukas@owncloud.com']);
+	public function testTo(): void {
 		$this->message->setTo(['lukas@owncloud.com']);
-	}
-
-	public function testGetTo() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('getTo')
-			->will($this->returnValue(['lukas@owncloud.com']));
-
 		$this->assertSame(['lukas@owncloud.com'], $this->message->getTo());
+		$this->assertEquals([new Address('lukas@owncloud.com')], $this->symfonyMail->getTo());
 	}
 
-	public function testSetCc() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('setCc')
-			->with(['lukas@owncloud.com']);
-		$this->message->setCc(['lukas@owncloud.com']);
+	public function testReplyTo(): void {
+		$this->message->setReplyTo(['lukas@owncloud.com']);
+		$this->assertSame(['lukas@owncloud.com'], $this->message->getReplyTo());
+		$this->assertEquals([new Address('lukas@owncloud.com')], $this->symfonyMail->getReplyTo());
 	}
 
-	public function testGetCc() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('getCc')
-			->will($this->returnValue(['lukas@owncloud.com']));
-
+	public function testCC(): void {
+		$this->message->setCc(['lukas@owncloud.com']);
 		$this->assertSame(['lukas@owncloud.com'], $this->message->getCc());
+		$this->assertEquals([new Address('lukas@owncloud.com')], $this->symfonyMail->getCc());
 	}
 
-	public function testSetBcc() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('setBcc')
-			->with(['lukas@owncloud.com']);
+	public function testBCC(): void {
 		$this->message->setBcc(['lukas@owncloud.com']);
-	}
-
-	public function testGetBcc() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('getBcc')
-			->will($this->returnValue(['lukas@owncloud.com']));
-
 		$this->assertSame(['lukas@owncloud.com'], $this->message->getBcc());
+		$this->assertEquals([new Address('lukas@owncloud.com')], $this->symfonyMail->getBcc());
 	}
-
-	public function testSetSubject() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('setSubject')
-			->with('Fancy Subject');
-
+	public function testSubject(): void {
 		$this->message->setSubject('Fancy Subject');
-	}
-
-	public function testGetSubject() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('getSubject')
-			->will($this->returnValue('Fancy Subject'));
-
 		$this->assertSame('Fancy Subject', $this->message->getSubject());
+		$this->assertEquals('Fancy Subject', $this->symfonyMail->getSubject());
 	}
 
-	public function testSetPlainBody() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('setBody')
-			->with('Fancy Body');
-
+	public function testSetPlainBody(): void {
 		$this->message->setPlainBody('Fancy Body');
+		self::assertEquals('Fancy Body', $this->symfonyMail->getTextBody());
 	}
 
-	public function testGetPlainBody() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('getBody')
-			->will($this->returnValue('Fancy Body'));
-
+	public function testGetPlainBody(): void {
+		$this->symfonyMail->text('Fancy Body');
 		$this->assertSame('Fancy Body', $this->message->getPlainBody());
 	}
 
-	public function testSetHtmlBody() {
-		$this->swiftMessage
-			->expects($this->once())
-			->method('addPart')
-			->with('<blink>Fancy Body</blink>', 'text/html');
-
+	public function testSetHtmlBody(): void {
 		$this->message->setHtmlBody('<blink>Fancy Body</blink>');
+		self::assertEquals('<blink>Fancy Body</blink>', $this->symfonyMail->getHtmlBody());
 	}
 }