Spam filtering on your own mail server is easy. 99% of spam are generic automated E-Mails that are sent in bulk with lots of spoofed metadata (domain, sending address, date, etc.). I have an address on a domain that used to be hosted by a third party and it got tons of spam. At some point I moved the domain to my own server with mailcow, and it blocked the vast majority of spam out of the box with no false positives. It uses rspamd, not sure if they have a tweaked config for it or something

Generally I really like mailcow. It makes dealing with all the ugly parts of hosting E-Mail fairly simple