Not exactly a how-to, but i know no better place.
I ran into a couple of email providers which might be worth to look at:
https://www.mailoo.org/http://ninthfloor.org/joinhttp://privatdemail.net/en/https://www.safe-mail.net/cgi-bin/Safe- ... a-7e60576fand a list at:
https://anonymous-proxy-servers.net/en/ ... vider.htmlassuming one is not happy with riseup for this reason or another. tails has listed two other providers, i will add them asap.
I found another list of providers:
http://prxbx.com/email/I got experience with none of them. I simply ran into the links.