The Exchange 2000 Server has been set up for 2 SMTP domains (similar to "Hosting mulitple SMTP Domains on Exchange 2000 on http://www.msexchange.org/, Jul 10 and according to http://www.christensen-software.de/support/installexchg2000.asp - unformtunately in German). However, the primary domain XY seems not to be recognised by Exchange when you send messages from user1@XY to user2@XY, as revealed by the following event- logging messages: Source: MS Exchange Transport Category: Queuing Engine Event: 4004 Description: "Categorization failed. The error message is: the specified domain does either not exist or cannot be contacted." and another similar message: "Message delivery to the remote domain XY failed for the follwoing reason: the connection was dropped by the remote host". However, sending messages from user1@XY to anyuser@any_outside_domain is working. Receiving, however, is not working at all. Looking forward to advice, Gerhard