I have Exchange Server 2003. Currently there are 7 users sharing various Celndars. They are also setup with their mailbox account and an external POP3 account. When they send emails I would like to specify the external POP3 accounts and when they send invitations and respond to those invitations I would like to specify the server.local mailbox account. Is there anyway to do this automatically, without having to educate the users as to which account to use and when?