I want to clarify that message further. The users are normally dialing through an ISP of their choice. They then run Outlook (either express or just plain Outlook) and send messages to users in the domain and and to external users as well. Domain users will get the message. However, users not in the domain (for instance Yahoo.com) will not go through and the users then get the bounce message I pasted earlier. What could be causing this problem? I've checked and checked all settings that I believe may be responsible and for the life of me can't figure it out! Cheers, Anthony.