Your log shows all emails are considered as SPAM by Amavisd, so you can try below solutions:
*) Block this sender if possible. You can add blacklisted senders with iRedAdmin-Pro if blacklist management is available under menu "System -> Blacklist".
*) If you have iRedAdmin-Pro installed, configure Amavisd to quarantine SPAM into SQL server, then manage quarantined mails with iRedAdmin-Pro. You can either release them to users, or delete them without delivering to users' mailboxes. Reference: http://www.iredmail.org/wiki/index.php? … ining.SPAM