IMAP is incredibly annoying. To send a message, you send via SMTP and then upload that message to your Sent folder, so it's transferred twice. For some reason the IMAP implementation I use means that when I move a message to a different folder, it uploads the message to the new folder, deletes the original message, and then downloads the message from the new folder. I have no idea if it's my server, client or the spec, but very wasteful and often fucks up.