Strange but recurringly true: Win2K SP4 server running Exchange 5.5 SP4 member server in NT4 domain. This is an IMC and OWA server (no mailboxes) and no additional software besides McAfee (no On Access and no EPO) and Antigen. Periodically the server will just stop resolving external domain names to IP addresses (internal name resolution never fails and internal connectivity is never affected). If we change the IP address then instantly things all start up working. We have been battling this issue off and on for the last ~6 months and have only finally managed to make these concrete associations. Have contacted MS PSS 3 times, and 3 times have had our fee of $245 refunded for lack of issues detectable by them. We have tried a number of things, and checked lots of variables - so to list them all would be unnecessarily verbose (I have more respect for the list than that). I will attempt to reply with full and concise answers if you have any suggestions. I will tell you that we sit behind a PIX 520 that was running v4.X OS which we recently upgraded to v6.23 in hopes of resolving these issues. Any suggestions or fresh impressions would be greatly appreciated. Keith Beahm, Network Engineer Stinson Morrison Hecker, LLP kbeahm@xxxxxxxxxxxxxxxxx <mailto:kbeahm@xxxxxxxxxxxxxxxxx> 816.691.3374 Desk 816.918.0988 Cell 140*73*707 Nextel