I second mailcow. It’s what I’ve been using for years and it’s pretty great.
One thing I’ll add is before you take the plunge, make sure your VPS address isn’t on a block list somewhere. Pay a visit to mxtoolbox.com and you should find some resources there.
Check out ersatztv.org. That software lefts you create custom, continuously playing channels that you can watch from Jellyfin as a live TV channel.