We did have issues with STunnel but in that thread was this which works!

"Google actually accepts non-SSL SMTP connections on one of their servers, aspmx.l.google.com on port 25. Set the Xerox to send via that and set your username and password to a Google Apps account. "

So, set the mail server to: aspmx.l.google.com and the port to 25 with the Server Requires Authentication unchecked and it should work.

I hope this is helpful for other users trying to find a solution.