@xavier_hm Fastmail is standard email - you can use any email client, you can back-up, export and import easily. But that means that their servers can read your email at any time. Proton is encrypted by their email clients, which on one hand means their servers can't see email contents except when receiving them, but which also means you can't use any other clients (e.g. Apple Mail) and that search is less powerful. And anyway if you're sending email to or receiving it from Gmail or Outlook, it could be scanned on that side.

IMO there isn't a big practical difference in security and privacy as long as you're not a high-profile target. Proton is theoretically more difficult to get access to your data, but in practice the adversary could use an exploit on your phone/device or force-feed you a cracked client that neutralizes encryption or something.

Personally I am on Fastmail but I think either is fine and neither is perfect (or perfectly secure).