I’d like to be able to “automate” email activity including re-writing subject lines, changes to From, To, CC, Bcc, Reply-to and so on. Also, copy or move attachnents to folders. Highlighting, flagging, notifications including sounds, bubbles, badges and such.
Do that on the server. It is not a good idea doing it on the client side, because depending on which client connects first, the rules could be different.