We have a three server environment. One front end server, two backend servers in active passive mode. The load on the servers is light with only 600 users.Version is Exchange Enterprise 2003 service pack 2 running on Windows server advanced server 2003.Servers were running normal until I finished uploading new Symantec Antivirus for Exchange license files. When I switched over to the passive server to upload the antivirus license file I noticed the"Exchange HTTP Virtual Server Instance 100 (POSTMASTER)" would not start.Event Viewer is only giving the following event 1005 Exchange HTTP Virtual Server Instance 100 (POSTMASTER): The IsAlive check for this resource failed. The service will not start no matter what server is active or passive.any help would be greatthanksMike

Hi,Have you checked article below:Incoming mail flow stops, or the SMTP service fails when you try to fail over a node in Exchange Server 2003 or in Exchange 2000 Server after you install McAfee VirusScan Enterprisehttp://support.microsoft.com/kb/908864Regards,Xiu