The domain situation is something that I don't have a good understanding on, and part of the reason why I outsource the responsibility to a third party email provider - namely that they will do a better job protecting their own domain, than I'd do protecting mine.

I understand that some domains carry some legal attachment. That the new vanity domains are not as trustworthy as others, some are even filtered, as email validators reject it for not being a "valid" address even. Some TLDs need to have a business registered on a location, etc. And I understand that the oldest ones (com, org, net) are among the most universally accepted. But I don't know what carries greater risk: 1. me losing control over my domain, or 2. me losing access to my email account (Posteo in particular - I wouldn't just trust any email provider).