vim /etc/fail2ban/jail.d/postfix.local
action = nftables-multiport[name=postfix, port="80,443,25,587,465,110,995,143,993,4190", protocol=tcp]
banned_db[name=postfix, port="80,443,25,587,465,110,995,143,993,4190", protocol=tcp]
sendmail[name=Postfix, dest=user@domain.com, sender=root]
service fail2ban restart
https://forum.iredmail.org/topic9644-fail2ban-blocked-ips.html