[maggit]

An unfortunate reality is that IMAP is a really bad protocol. I encourage you to try implementing a client to get a feel for how difficult and quirky the protocol is. (Be sure to try implementing IDLE)

I'd love to see a better base protocol with a clean extension mechanism and a culture of documenting and publishing such extenstions. One can dream :)

[exelius]

EWS (Exchange Web Services) is actually a very good and well-documented protocol built on top of HTTP/HTTPS. Unfortunately, it's Microsoft only, but it's the closest anyone's really come to a "modern" e-mail protocol.