[blfr]

If you like Proton features and want to move away from Gmail, consider Mailpile[1]. It's almost ready, there's a release candidate and packages for Debian/Ubuntu; it offers to protect your data with a master password like Proton; it supports GPG which with all its problems is still the way to encrypt your emails; and you can run it on your own server. Best of all it's open source and written in Python. You can know exactly what it does with your messages.

Mailpile is an email client (MUA) so you will need a server (MTA). At first you can try it out with your regular ISP, even Gmail. Later you can set up your own server. Setup is a little involved but much less than people tell you and, if you choose a competently run distro, requires very little ongoing maintenance.

With your own server, you can have it working exactly as you like. Export feature? No problem, you have direct access to the maildir, mailbox or the database. Want a catch-all? One switch in the config. You will have little trouble finding a provider who accepts your preferred method of payment, too.

[1] https://www.mailpile.is/

[the_common_man]

There is also cloudron.io. It has imap/smtp/sieve/catch-all/relaying/aliases/tagging/rest api. Fairly complete. https://cloudron.io/documentation/email/

[nullwarp]

My only complaint with cloudron is that the auto-update mechanism requires a subscription. You can manually upgrade, but it's awkward and I broke it more than once while trying.

[type0]

Can you use one subscription to update multiple cloudron VPS servers or would you need to have a separate for each one?