qpsmtpd 0.94-4 (arm64 binary) in ubuntu kinetic

 This is a replacement SMTP daemon which installs alongside a mail delivery
 and transport system such as Exim, Postfix or Qmail, or used as an SMTP
 proxy for a remote/DMZ MTA.
 .
 The qpsmtpd damon emphasizes spam detection during the SMTP transaction,
 attempting to reach spam/nonspam decisions prior to accepting each message,
 thereby eliminating much bounce/forgery blowback. It exploits its visbility
 into the network transaction to detect certain behaviors often exhibited by
 spam sending agents.
 .
 Qpsmtpd is written in Perl, with an extensive plugin API making it easy to
 add new features or replace functional components.