Able to pull through email info through header

app/mailers/application_mailer.rb

@@ -8,4 +8,23 @@ class ApplicationMailer < Mail::Notify::Mailer
       "GOVUK_NOTIFY_TEMPLATE_ID_APPLICATION",
       "95adafaf-0920-4623-bddc-340853c047af",
     )
+
+    rescue_from Notifications::Client::RequestError do
+      # WARNING: this needs to be a block, otherwise the exception will not be
+      # re-raised and we will not be notified via Sentry, and the job will not retry.
+      #
+      # @see https://github.com/rails/rails/issues/39018
+      if respond_to?(:headers)
+        binding.break
+        email = Email.find(headers['email-log-id'].to_s)
+        email.update!(delivery_status: 'notify_error')
+      end
+
+      raise
+    end
+
+    def notify_email(headers)
+      headers = headers.merge(rails_mailer: mailer_name, rails_mail_template: action_name)
+      view_mail(GOVUK_NOTIFY_TEMPLATE_ID, headers)
+    end
 end

app/views/anonymous/test_notify_error.text.erb

@@ -0,0 +1 @@
+This is used by the ApplicationMailer spec.

spec/mailers/application_mailer_spec.rb

@@ -0,0 +1,30 @@
+require 'rails_helper'
+
+RSpec.describe ApplicationMailer, :sidekiq do
+  describe '.rescue_from' do
+    fake_mailer = Class.new(ApplicationMailer) do
+      self.delivery_method = :notify
+      self.notify_settings = {
+        api_key: 'not-real-e1f4c969-b675-4a0d-a14d-623e7c2d3fd8-24fea27b-824e-4259-b5ce-1badafe98150',
+      }
+
+      def test_notify_error
+        notify_email(
+          to: '[email protected]',
+          subject: 'Some subject',
+        )
+      end
+    end
+
+    it 'marks errors as failed and re-raises the error' do
+      stub_request(:post, 'https://api.notifications.service.gov.uk/v2/notifications/email')
+        .to_return(status: 404)
+
+      expect {
+        fake_mailer.test_notify_error.deliver_now
+      }.to raise_error(Notifications::Client::NotFoundError)
+
+      expect(Email.last.delivery_status).to eql('notify_error')
+    end
+  end
+end