Issue Mails to a specific mail account get stuck in mail queue

[King555]

Server operating system version

Ubuntu 18.04.6 LTS x64

Plesk version and microupdate number

Plesk Obsidian 18.0.48 web admin edition

I have a mail account with no mailbox, one alias address and a forwarding to another mail account (with mailbox and another domain) on the server. Something like:
[email protected] ([email protected]) => [email protected]

And, maybe it's relevant, the spam filter is enabled and has the settings: mark spam messages, score 50 and whitelist *@* (this seems to be a way to disable greylisting for one specific mail address, when you don't want to disable it for the domain).

Whenever a mail arrives for [email protected] or [email protected], it appears at Tools & Settings - Server-wide mail settings - Mail Queue. And there these mails are stuck forever (at least several days, before I deleted them from the queue). Sometimes, but not everytime, the mail is still forwarded, although the entry in the queue is there.

I tried to reproduce it with a completely new mail account with exactly the same settings (but other names, of course), but then I did not have this issue.

What could be the problem here?

 

[King555]

After I deleted the mail account and re-created it with exactly the same settings, no mails appear in the mail queue anymore. So the problem is fixed.

But one type of mail was the daily DMARC report from Microsoft, which almost never arrived and always got stuck in the queue. Now it is rejected and I don't know why. Maybe it also was rejected before, but it stayed in the queue anyway.

Is this a bug with internal forwarding of mails when DMARC is enabled? I know there is a bug with completely internal mails (since years), but the Microsoft mails are from external, of course. Or is this just the way DMARC works? MS sends mail to my account #1, this mail is forwarded to account #2, then my mail server sees that MS does not allow that my account #1 can send mails on behalf of MS and my DMARC filter rejects the mail.

 

[King555]

Meanwhile also the last problem is solved. Well, not "solved", but answered. The DMARC aggregate reports from Microsoft are malformed in a way that it's quite "normal" that they are rejected, according to several sites on the web. Reports from Google and Yahoo arrive, so I guess everything is configured properly on my side.