Issue DKIM signature unverified

[Netbela]

Server operating system version

Ubuntu 20.04.4 LTS

Plesk version and microupdate number

Version 18.0.44 Update #3

Hi all,

I am trying to setup DKIM on my Plesk server however if I use the mxtoolbox email deliverability tool to chekc compliance I keep getting the 'DKIM Authenticated' failed. Due to the lack of DKIM signature some of the emails I send end up in customers mail spam boxes.

The domains are hosted on the Plesk server so I do not use any external DNS servers. The DKIM records are automatically created on the domain and seem to be OK, I have tested this with multiple DKIM checker tools. The MX records of the domains point to mail.<domainName>. This MX Record points to an A-record that in turn points to the IP of the Plesk server. I am using Postfix as mailserver and am running Plesk Obsidian Web Pro edition (Version 18.0.44 Update #3). Has anyone else encountered these issues with DKIM before? Should I change the MX-records to point to 'mail.pleskserver.com'?

This is what is seen in the Plesk mail log browser:
9E7C53E740: DKIM verification (d=tdomain-name.nl, 1024-bit key) failed: signature verification failed


If you need me to provide any more details then please let me know.

Kind regards,

Tom

 

[Netbela]

Related to this question, a mxtoolbox report can be found here:

Email Header Analyzer, RFC822 Parser - MxToolbox

mxtoolbox.com

I've just noticed this in the 'Authentication-Results':
Authentication-Results: ttwl.nl (amavisd-new); dkim=fail (1024-bit key)
reason="fail (bad RSA signature)" header.d=tinux-it.nl

Can it perhaps be that my amavis is not setup correctly or does something with the email body? If so, how do I correctly setup the anti-spam/anti-virus for Plesk mail server running postfix?