Just to be clear, are the other users having problems trying to send *from*
Exchange (on SBS) to an external account??? Your post was unclear as to
what you were trying to accomplish.
Just as an FYI, I don't recommend allowing pop3 in the network. All email
should be going through Exchange and Exchange should have antivirus
protection installed. Otherwise you've allowed a significant attack vector
in your network....actually several attack vectors...actually several for
every machine that you are allowing pop3 connections.
Work email for work. Personal email stays home. Migrating from an ISP
account to exchange can be done with the pop3 connector so it still gets the
benefits of Exchange.