I'm likely woefully uninformed on this, so I'd like to ask for some information. Last I heard/looked (many years ago), Proton was just webmail-only, I think. Can it actually do all the same things Fastmail can, as in IMAP/SMTP access, catch-all addressing (*@mydomain.tld routes to [email protected]; I'm the only user and own the entire domain, allowing me to do stuff like [email protected], [email protected], [email protected] and so on; so I know who's up to shady sh!t), MX records for a custom domain, built-in spam filtering, custom user-editable rules, 2fa, per-app passwords, and so on?

Because if it's got close to 1:1 feature parity (or better) I might consider a switch once my existing paid plan is up.

IMAP/SMTP isn’t really possible because it’s not E2E encrypted. You must use a protonmail client, or use their bridge application which encrypts/decrypts mail as it arrives/leaves your computer via IMAP/SMTP.

Protonmail has IMAP if you're a paying subscriber.

They don’t mention IMAP in the pricing page.

You're right. I thought Protonmail Bridge was IMAP support, but it isn't.

If you care about privacy, use a provider in a country with strong privacy laws. If you don't care, just use Gmail or Microsoft? I really don't see where Fastmail fits in here, unless you're Australian.

IMAP/JMAP.