Retrieve email key from X-Envelope-To header

changelogs/unreleased/jh-allow-x-envelope-to-header.yml

+---
+title: Support X-Envelope-To header as a location for Service Desk key
+merge_request: 40001
+author:
+type: fixed

lib/gitlab/email/receiver.rb

@@ -54,7 +54,8 @@ module Gitlab
       def key_from_additional_headers(mail)
         find_key_from_references(mail) ||
           find_key_from_delivered_to_header(mail) ||
-          find_key_from_envelope_to_header(mail)
+          find_key_from_envelope_to_header(mail) ||
+          find_key_from_x_envelope_to_header(mail)
       end
 
       def ensure_references_array(references)
@@ -91,6 +92,13 @@ module Gitlab
         end
       end
 
+      def find_key_from_x_envelope_to_header(mail)
+        Array(mail[:x_envelope_to]).find do |header|
+          key = Gitlab::IncomingEmail.key_from_address(header.value)
+          break key if key
+        end
+      end
+
       def ignore_auto_reply!(mail)
         if auto_submitted?(mail) || auto_replied?(mail)
           raise AutoGeneratedEmailError

spec/fixtures/emails/x_envelope_to_header.eml

+Return-Path: <jake@example.com>
+Received: from myserver.example.com ([unix socket]) by myserver (Cyrus v2.2.13-Debian-2.2.13-19+squeeze3) with LMTPA; Thu, 13 Jun 2013 17:03:50 -0400
+Received: from mail.example.com (mail.example.com [IPv6:2607:f8b0:4001:c03::234]) by myserver.example.com (8.14.3/8.14.3/Debian-9.4) with ESMTP id r5DL3nFJ016967 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for <incoming+gitlabhq/gitlabhq@example.com>; Thu, 13 Jun 2013 17:03:50 -0400
+Received: by myserver.example.com with SMTP id f4so21977375iea.25 for <incoming+gitlabhq/gitlabhq@appmail.example.com>; Thu, 13 Jun 2013 14:03:48 -0700
+Received: by 10.0.0.1 with HTTP; Thu, 13 Jun 2013 14:03:48 -0700
+From: "jake@example.com" <jake@example.com>
+To: "support@example.com" <support@example.com>
+Subject: Insert hilarious subject line here
+Date: Tue, 26 Nov 2019 14:22:41 +0000
+Message-ID: <7e2296f83dbf4de388cbf5f56f52c11f@EXDAG29-1.EXCHANGE.INT>
+Accept-Language: de-DE, en-US
+Content-Language: de-DE
+X-MS-Has-Attach:
+X-MS-TNEF-Correlator:
+x-ms-exchange-transport-fromentityheader: Hosted
+x-originating-ip: [62.96.54.178]
+Content-Type: multipart/alternative;
+	boundary="_000_7e2296f83dbf4de388cbf5f56f52c11fEXDAG291EXCHANGEINT_"
+MIME-Version: 1.0
+X-Envelope-To: incoming+gitlabhq/gitlabhq+auth_token@appmail.example.com
+
+--_000_7e2296f83dbf4de388cbf5f56f52c11fEXDAG291EXCHANGEINT_
+Content-Type: text/plain; charset="iso-8859-1"
+Content-Transfer-Encoding: quoted-printable
+
+
+
+--_000_7e2296f83dbf4de388cbf5f56f52c11fEXDAG291EXCHANGEINT_
+Content-Type: text/html; charset="iso-8859-1"
+Content-Transfer-Encoding: quoted-printable
+
+Look, a message with some alternate headers! We should really support them.

spec/lib/gitlab/email/receiver_spec.rb

@@ -36,6 +36,12 @@ RSpec.describe Gitlab::Email::Receiver do
       it_behaves_like 'correctly finds the mail key'
     end
 
+    context 'when in an X-Envelope-To header' do
+      let(:email_raw) { fixture_file('emails/x_envelope_to_header.eml') }
+
+      it_behaves_like 'correctly finds the mail key'
+    end
+
     context 'when enclosed with angle brackets in an Envelope-To header' do
       let(:email_raw) { fixture_file('emails/envelope_to_header_with_angle_brackets.eml') }