Currently thinking about either Tuta or Mailbox.org, but to be honest, I don’t even know many providers.
Something I do not like is limit on number of addresses with a custom domain. Mailbox is at least a bit reasonable with 50 on Standard, but Proton’s 10 on Mail Plus is disqualifying for me.
Tuta has unlimited number, but doesn’t support PGP.
So I plan to check out whatever you guys use.
Also if your ISP puts your IP on the PBL. They also don’t like it if your reverse lookup doesn’t match your domain. I was able to send from my IP for a while and then Google stopped delivering my mail with the PBL given as the reason. Other destinations may be less picky but Google has a lot of requirements some of which are out of your hand unless you have a static IP.
I think all email services should be required to list their delivery requirements publicly.
I just ended up using the free plan of a relay that allows more on their free plan than I’ll ever used in a month.