http://www.ipswitch.com/support/imail/guide/2006/imail_server_wh/service s_imail_smtp_settings.htm
Disregard, I found this No Mail Relay. Selecting this option from the list box enables the SMTP server to refuse to accept mail destined for other hosts (any host not on the IMail server), unless the user authenticates. Select this option if all of your users send and receive mail from the same host that IMail Server is on, or if they use web messaging to access mail. You will still receive mail for local users because a message destined for or originating from the IMail Server host does not use the relay function. Question now become how to require authentication no matter what. Thanks
