I have dealt with web hosting for many years now. SmarterMail is the only email server software comes with IDS. In case you didn’t know what is IDS? IDS is normally found in firewall known as intrusion detecting system. IDS has a set of rules if any connection has violated the rules, mitigation will kick in. They serve to minimize the risk of a server’s attack or hack.
SmarterMail as this to stop abnormal activities, like attempting to log in with failed passwords known as brute-force or similar. This has greatly reduced a compromised email account or server’s abuse. Base on my experience, SmarterMail email server has very low a compromised email account uses to send spam emails. Thanks to the IDS in SmarterMail.