fix: do not remove contents from Schleuder ML messages

src/headerdef.rs

@@ -38,6 +38,9 @@ pub enum HeaderDef {
     /// Mailing list ID defined in [RFC 2919](https://tools.ietf.org/html/rfc2919).
     ListId,
     ListPost,
+
+    /// List-Help header defined in [RFC 2369](https://datatracker.ietf.org/doc/html/rfc2369).
+    ListHelp,
     References,
 
     /// In-Reply-To header containing Message-ID of the parent message.

src/mimeparser.rs

@@ -1365,6 +1365,15 @@ impl MimeMessage {
         self.get_mailinglist_header().is_some()
     }
 
+    /// Detects Schleuder mailing list by List-Help header.
+    pub(crate) fn is_schleuder_message(&self) -> bool {
+        if let Some(list_help) = self.get_header(HeaderDef::ListHelp) {
+            list_help == "<https://schleuder.org/>"
+        } else {
+            false
+        }
+    }
+
     pub fn replace_msg_by_error(&mut self, error_msg: &str) {
         self.is_system_message = SystemMessage::Unknown;
         if let Some(part) = self.parts.first_mut() {
@@ -1593,8 +1602,12 @@ impl MimeMessage {
     /// eg. when the user-edited-content is html.
     /// As these footers would appear as repeated, separate text-bubbles,
     /// we remove them.
+    ///
+    /// We make an exception for Schleuder mailing lists
+    /// because they typically create messages with two text parts,
+    /// one for headers and one for the actual contents.
     fn maybe_remove_inline_mailinglist_footer(&mut self) {
-        if self.is_mailinglist_message() {
+        if self.is_mailinglist_message() && !self.is_schleuder_message() {
             let text_part_cnt = self
                 .parts
                 .iter()
@@ -3786,4 +3799,24 @@ Content-Disposition: reaction\n\
 
         Ok(())
     }
+
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn test_schleuder() -> Result<()> {
+        let context = TestContext::new_alice().await;
+        let raw = include_bytes!("../test-data/message/schleuder.eml");
+
+        let msg = MimeMessage::from_bytes(&context.ctx, &raw[..], None)
+            .await
+            .unwrap();
+        assert_eq!(msg.parts.len(), 2);
+
+        // Header part.
+        assert_eq!(msg.parts[0].typ, Viewtype::Text);
+
+        // Actual contents part.
+        assert_eq!(msg.parts[1].typ, Viewtype::Text);
+        assert_eq!(msg.parts[1].msg, "hello,\nbye");
+
+        Ok(())
+    }
 }

test-data/message/schleuder.eml

@@ -0,0 +1,66 @@
+Return-Path: <[email protected]>
+Delivered-To: [email protected]
+Date: Tue, 02 Jan 2024 05:00:00 +0000
+From: [email protected]
+Sender: [email protected]
+To: [email protected]
+Message-ID: <[email protected]>
+In-Reply-To: 
+References: 
+Subject: [REPOST] Some subject
+Mime-Version: 1.0
+Content-Type: multipart/signed;
+ boundary="--==_mimepart_65938a80866e8_663a2abed9b585c064398";
+ micalg=pgp-sha1;
+ protocol="application/pgp-signature"
+Content-Transfer-Encoding: 7bit
+List-Id: <mailing-list.example.org>
+List-Owner: <mailto:[email protected]> (Use list's public
+ key)
+List-Help: <https://schleuder.org/>
+List-Post: <mailto:[email protected]>
+
+This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
+----==_mimepart_65938a80866e8_663a2abed9b585c064398
+Content-Type: multipart/mixed;
+ boundary="--==_mimepart_65938a8086476_663a2abed9b585c0642c7";
+ charset=UTF-8
+Content-Transfer-Encoding: 7bit
+
+
+----==_mimepart_65938a8086476_663a2abed9b585c0642c7
+Content-Type: text/plain;
+ charset=UTF-8
+Content-Transfer-Encoding: 7bit
+
+From: [email protected]
+To: [email protected]
+Cc: 
+Date: Tue, 02 Jan 2024 05:00:00 +0000
+Sig: Unsigned
+Enc: Unencrypted
+
+----==_mimepart_65938a8086476_663a2abed9b585c0642c7
+Content-Type: text/plain;
+ charset=utf-8
+Content-Transfer-Encoding: quoted-printable
+
+hello,
+bye
+
+----==_mimepart_65938a8086476_663a2abed9b585c0642c7--
+
+----==_mimepart_65938a80866e8_663a2abed9b585c064398
+Content-Type: application/pgp-signature;
+ name=signature.asc
+Content-Transfer-Encoding: 7bit
+Content-Disposition: attachment;
+ filename=signature.asc
+Content-Description: OpenPGP digital signature
+
+-----BEGIN PGP SIGNATURE-----
+
+REDACTED
+-----END PGP SIGNATURE-----
+
+----==_mimepart_65938a80866e8_663a2abed9b585c064398--