Issue Change DKIM Signature mail headers

[vargasia]

Server operating system version

Debian 12

Plesk version and microupdate number

18.0.71 #4

Hi there.

I noticed an issue with the DKIM signature Plesk generates.

The DKIM-Signature header includes this:
h=Received:Received:From:To:Subject;

Two problems here:

1. The Received header is repeated twice.
2. Important headers like Date, Message-ID, and MIME-Version are completely missing from the signed headers list.

This weakens the DKIM signature and causes Hotmail/Outlook to reject or mark the DKIM as invalid, even though other providers accept it fine.

I suspect Plesk’s DKIM signing component is not properly configuring which headers to sign, or there’s a bug causing header duplication and omission.

Can someone confirm this is a known issue? Is there a fix or a way to customize which headers get signed in Plesk’s DKIM?

Thanks in advance.

 

[burnley]

@Sebahat.hadzhi Is there a way to customise what fileds are DKIM signed in the email headers, either via a configuration file or panel.ini entry perhaps? By default Plesk seems to use a minimal set h=From:To:Subject; and possibly Recieved. We see that Plesk has its own internal DKIM signing milter for this but there appears to be no relevant documentation on how to adjust it.

This been raised by several clients now as a result of security audits so we are investigating what can be done to tighten security.

 

[nmdpa3]

There have been numerous changes to DKIM since 18.0.71 #4 - https://docs.plesk.com/release-notes/obsidian/change-log/