Proxmox Mail Gateway : How to add Subject Information to the log

I have Proxmox Mail Gateway (PMG) and I need to add subject information to the log. This subject is needed to get detailed information about the email that has been sent. So, I can trace the email in the log with this message trace.

Below is what I did

Go to RuleDB folder

cd /usr/share/perl5/PMG/RuleDB

Backup Accept.pm

cp Accept.pm Accept.pm-ori

Open Accept.pm

vi Accept.pm

Add this line before “if ($qid) {” (line 126)

syslog('info', "$qid: warning: header Subject: %s from $msginfo->{fqdn}", PMG::Utils::decode_rfc1522(PVE::Tools::trim($entity->head->get('subject'))) || 'No Subject');

So the line will be like this

Restart pmg-smtp-filter

systemctl restart pmg-smtp-filter

Now, you can see the subject information on the log

Feb 14 21:18:01 pmg pmg-smtp-filter[13026]: 80CA81C1076: warning: header Subject: Test sending email to imanudin.net from pmg.imanudin.web.id
Feb 14 21:18:01 pmg pmg-smtp-filter[13026]: 1C107563EB981976CAC: accept mail to  (80CA81C1076) (rule: default-accept)

And you can trace with the zmmsgtrace script here: How To Add Subject Information on Message Trace

The results

/srv/zmmsgtrace /var/log/mail.log

Tracing messages

Message ID '20230214211801.007912@ThinkPad-X230'
Subject 'Test sending email to imanudin.net'
admin@imanudin.web.id -->
	admin@imanudin.net
  Recipient admin@imanudin.net
  Feb 14 21:18:01 - localhost.localdomain (127.0.0.1], orig_client=unknown[192.168.1.11) --> 192.168.1.21:25 (192.168.1.21:25) status sent

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Good luck 🙂