clamav scans for viruses/malware/etc and it's not designed for what you need.
If you already have implemented SpamAssassin you can use that one for your purpose and/or other regexp milter.
-------- Original message --------
From: PGNet Dev via clamav-users <clamav-users@lists.clamav.net>
Date: 5/28/20 23:07 (GMT+02:00)
To: ClamAV users ML <clamav-users@lists.clamav.net>
Cc: PGNet Dev <pgnet.dev@gmail.com>, David Beecher <dbeecher@tekops.com>
Subject: Re: [clamav-users] milter
On 5/28/20 12:39 PM, David Beecher via clamav-users wrote: