[billyruffian]

I love (and donate to) mailcow, it's an amazing piece of work which makes it simple to get up and running and to maintain a email stack.

The problems you end up with is dealing with the big fish in this space. For instance, Microsoft are currently blocking all/most/a lot-of mail from Linode IPs and have been since 21 Dec regardless of individual server reputation[0].

[0] https://www.linode.com/community/questions/22287/550-57511-a...