Merge branch...

Merge branch '39593-emails-on-push-are-sent-to-only-the-first-recipient-when-using-aws-ses' into 'master'

Resolve "Emails on Push are sent to only the first recipient when using AWS SES"

Closes #39593

See merge request gitlab-org/gitlab-ce!15083

changelogs/unreleased/39593-emails-on-push-are-sent-to-only-the-first-recipient-when-using-aws-ses.yml

+---
+title: Only set Auto-Submitted header once for emails on push
+merge_request:
+author:
+type: fixed

lib/additional_email_headers_interceptor.rb

 class AdditionalEmailHeadersInterceptor
   def self.delivering_email(message)
-    message.headers(
-      'Auto-Submitted' => 'auto-generated',
-      'X-Auto-Response-Suppress' => 'All'
-    )
+    message.header['Auto-Submitted'] ||= 'auto-generated'
+    message.header['X-Auto-Response-Suppress'] ||= 'All'
   end
 end

spec/lib/additional_email_headers_interceptor_spec.rb

 require 'spec_helper'
 
 describe AdditionalEmailHeadersInterceptor do
-  it 'adds Auto-Submitted header' do
-    mail = ActionMailer::Base.mail(to: 'test@mail.com', from: 'info@mail.com', body: 'hello').deliver
+  let(:mail) do
+    ActionMailer::Base.mail(to: 'test@mail.com', from: 'info@mail.com', body: 'hello')
+  end
+
+  before do
+    mail.deliver_now
+  end
 
+  it 'adds Auto-Submitted header' do
     expect(mail.header['To'].value).to eq('test@mail.com')
     expect(mail.header['From'].value).to eq('info@mail.com')
     expect(mail.header['Auto-Submitted'].value).to eq('auto-generated')
     expect(mail.header['X-Auto-Response-Suppress'].value).to eq('All')
   end
+
+  context 'when the same mail object is sent twice' do
+    before do
+      mail.deliver_now
+    end
+
+    it 'does not add the Auto-Submitted header twice' do
+      expect(mail.header['Auto-Submitted'].value).to eq('auto-generated')
+      expect(mail.header['X-Auto-Response-Suppress'].value).to eq('All')
+    end
+  end
 end