I'm running mailcow for about a year now. So far so good, very little to no maintenance and the update process through the dockerized version is very easy. Using it with a few friends and 10 custom domains with wildcard addresses, no issues with the spam-filter either.

I'm only slightly worried if they ever abandon the project I'm out of luck maintaining it by myself. But since it's all based on standard software it's rather easy so switch to another solution I guess.