How to protect your mail on postfix?

Question

Email

Such a task:
You need to redirect several mail servers through 1 host (MTA). Used by postfix and IBM lotus domino.
This MTA needs to be protected from spam (there was such a case that attackers, having gained access to our mail, sent spam, due to which all mail fell into blacklists). What solutions are available for such tasks? Preferably available from the centos repository

Answer 1

Postfix has built-in rate limits, but, unfortunately, they are only per IP and not per user. For more detailed limiting, you can use policyd
https://wiki.policyd.org/ or other filters that work with postfix via the Policy protocol
www.postfix.org/addon.html#policy