We have an exchange 200 server (sp2) on win2k (sp2) on Win2k domain A and an exchange 5.5 (sp4) on windows nt4 (sp6) on NT domain B. Both servers are in the same site/org. When an exchange 5.5 recipient sends email to an exchange 2000 recipient he gets an ndr stating recipient name is not recognised. When I look in the tracking logs it says message message submitted, \\exchange2000servername\trackinglogs\trackinglogddmmyy.log not found. Network name not recognised?? There is a two way trust between these domains and tracking is switched on. Any troubleshooting tips? Thanks folks. Leo