Fastmail is the creator of the JMAP protocol (now an IETF standard), [1] which is a much better successor to IMAP. IIRC, it also supports it on its servers. [1

Fastmail is the creator of the JMAP protocol (now an IETF standard), [1] which is a much better successor to IMAP. IIRC, it also supports it on its servers. [1]: https://jmap.io/ https://jmap.io/