Re: Used to run my own mail server 6 or 7 years ago, but stopped
One of the most common attacks I saw the last time I hosted a mail server (and this was years ago) were a huge amount of brute force attacks on IMAP ports. So much so that they were effectively a DoS.
dovecot can rate-limit login attempts, and iptables can rate-limit SYN connections. Between the two tools, you can make this a minor annoyance. fail2ban can take care of anything that doesn't get stopped by those, if that's your thing.
Also, the amount of inbound spam was an issue, it was somewhere around 30x legitimate mail volumes
That's a low level of spam compared to what most of us see. Again, you defeat spam by using tools, not the sweat of your brow.