One really nice advantage for Posteo is even if you stop paying, they'll never delete your account unless you specifically delete it yourself(preventing address recycling, unlike mailbox.org) and you can still access your account and recieve emails, you just can't send any until you pay again. They won't even delete it from inactivity.

That's a rather unique feature in the email world now.

Personally I switched to a private email just so it would be one less avenue to harvest my data and habits for advertisers.