I spent four hours on Google last night about this problem. Saw reports of the same messages, but not the same situation. SUMMARY: 3 separate servers upgraded from RH7.0 to RH7.3 - all can send/receive mail locally and to/from the outside world EXCEPT for/from each other - which was not a problem under RH7.0. Do not believe there are errors in config files, particularly /etc/mail/local-host-names, and I have read the part of the sendmail FAQ about "mail loops back to me" and it DOES NOT APPLY in this case. I've been through what sendmail documentation I can understand - can someone tell me what has changed somewhere prior to or at 8.11.6 which shipped with RH7.3 that might cause this? I have another identically hacked RH7.0 server which I hope to rebuild/upgrade tonight - it will be interesting to see if all FOUR servers have the same problem. I'm losing mail which is supposed to be forwarded between these servers. Dick