[simias]

I just use dovecot, postfix and spamassassin. It did take me many hours and a lot of googling to configure it but it's very low maintenance after that.

I don't have any problem getting my emails accepted by gmail and friends.

The trick is to use an IP range that's not "fishy" (that basically precludes hosting email on your home connection, everybody expects spam from those and they're blacklisted everywhere). Then use DKIM, SMTPS, DMARC, SPF and be very careful not to allow any kind of open relay for spammers and you should be mostly fine, at least in my experience.

There are many websites online that offer to test your email setup for obvious flaws (open relay, missing headers etc...), for instance https://www.mail-tester.com/ and https://mxtoolbox.com/diagnostic.aspx . You should also check if some blacklists have your IP or domain blacklisted for some reason, and then request a delisting (after making sure that you're actually not sending spam because of a bad config): https://mxtoolbox.com/blacklists.aspx

It's definitely not plug-and-play but it's pretty interesting if you don't mind system admin. You also have a lot of flexibility if you want to filter and automate your emails in any way. I was also pleasantly surprised by the efficiency of spamassassin, properly trained there are very few false negatives and almost no false positives.