Invalid Message-ID header when using BackendIMAP
No idea if this applies to other backends as I don’t have a suitable server for testing. I’m using the latest version of Z-Push from the official repositories on Debian Stretch. If I send an email using an ActiveSync, SpamAssassin on the receiving end adds the following warnings:
This is the message ID, which is indeed missing the domain:
I can confirm that the problem is specific to Z-Push, as when I send an email from the same account on the server, but using Roundcube instead, then the Message-ID header is correctly generated, including the domain.
This message ID is created by your phone. Z-Push just sends it out. I guess we would need some code to detect an incomplete message id and then append a domain name (to be configured?).
I think this is an IMAP only issue. This is most certainly working with the Kopano backend, but then there the sending process is completely different.
Curious. The device in question is an iPhone SE running iOS 11, which I would expect to follow the specs for sending mail. It’s also got another Z-Push account set up on it, linked to a Zarafa 7.2.6 install, which as you say does correctly set the Message-ID.