Which email providers on the superlist do you guys recommend as the most secure and anonymous?
The two most important aspects I'd be looking for are 1) longevity (most likely to be around for years) and 2) non-compliance with the 3 letter agency requests (if they request information, they will not or cannot hand over anything). A one-time lifetime subscription payment is OK as long as the other 2 points are met.
Protonmail.com meets both requirements. Zero knowledge so they couldn't comply with a warrant/subpoena even if they wanted. They also have critical mass now so they aren't going anywhere.