Mattermost-server: Improve email headers.

[MrSorcus]

Summary

Rspamd assign some spam points based on few email headers.

Steps to reproduce

Version 5.4.0.
Just get notification and look at source of email.

Expected behavior

MIME-version and Message-ID must be correct.

Observed behavior (that appears unintentional)

Screenshot from Rspamd. Here 2.90 / 15. If it be 5.90 / 15, soft reject will be applied.
If 15 / 15 - hard reject.
Mime-Version: 1.0 - here MIME must be capitalized (see https://tools.ietf.org/html/rfc4021#section-2.2.1)
Message-ID - must be received from Mattermost server (see https://tools.ietf.org/html/rfc4021#section-2.1.8)

[amyblais]

Hi @MrSorcus,

Giving you an update that I'm working on investigating this,

[amyblais]

I created a ticket for this here: https://mattermost.atlassian.net/browse/MM-13012.

[amyblais]

Hi @MrSorcus it looks like a PR was already opened in the gomail library for the MIME issue: https://github.com/go-gomail/gomail/pull/127.

For any further issues, it seems it would make sense to open an Issue in the gomail repo: https://github.com/go-gomail/gomail/issues. Would you be able to help with that?

[MrSorcus]

Would you be able to help with that?

Looks that here issue exists - https://github.com/go-gomail/gomail/issues/36
But it closed.

[MrSorcus]

If i understand correctly, there is only one way to implement it. In mattermost-server.

[amyblais]

Sounds good, the Jira ticket that I opened has been assigned to one of our developer teams and they will determine in the upcoming days how to proceed with a fix for this.