[jaykru]

posteo.de is great. Here's a good chart [1] comparing various providers with respect to privacy and other important factors. In my case, I went with Posteo because they offer the nice combination of anonymous payment method, located in Germany (so not as bad for my metadata as, say, five-eyes countries), and offering POP3/IMAP, so you can use your own client and have a local copy of my mail without any weird bridge software.

[1] https://thatoneprivacysite.net/email-comparison-chart/

[Tomte]

Don't allow your own domain, which should disqualify them. Especially since nobody knows whether they'll survive the next years.

Having a GMX address, fine. I wouldn't want it, but I'd expect them to be around in ten years. Posteo, who knows?