right, gmail works with all clients.
what raven wants to do is use gmail to in effect "host" the other email address. so when you send your mail as joe@comcast.net you can send it using your gmail interface.
This on the recieving side shows up as From: "joe@GMAIL.com sent on behalf of joe@COMCAST.net"
ive only seen it show up this way in OE but could show up in others.