I dont know how worthwhile this would be.. as with IM forwards you just set up your account with them, and it works for you without ever having to go back there. I guess you could possibly have it so you can check your messages forwarded to a special email for it with the expression. Like: have IM forwards forward to a special email (possibly make your own server to host these people messages). Have your expression be a pop3 (or something else) client that connects to the pop3 (or whatever) server and downloads all your emails (offline messages).