This email provider gives onion email addresses:

pflujznptk5lmuf6xwadfqy6nffykdvahfbljh7liljailjbxrgvhfid.onion

Take care when creating the username to pull down the domain list and choose the onion domain. That address you get can then be used to receive messages. Unlike other onion email providers, this is possibly the only provider who offers addresses with no clearnet variations. So if a recipient figures out the clearnet domain it apparently cannot be used to reach you. This forces Google and MS out of the loop.

It’s narrowly useful for some situations where you are forced to provide an email address against your will (which is increasingly a problem with European governments). Though of course there are situations where it will not work, such as if it’s a part of a procedure that requires confirmation codes.

Warning: be wary of the fact that this ESP’s clearnet site is on Cloudflare. Just don’t use the clearnet site and keep CF out of the loop.