Thanx Ching, Let me tell you that I have disabled the TCP/IP on the Internal network Card due to the install of Service pack 4 of Exchange server. If I bind both the cards to TCP/IP, then MTA does not start and gives error no 9266. I have followed the reccommended solution from Microsoft also, but to no avail. So all the 40 odd clients connect to Exchange server with NETBEUI protocol only. Yes, I have WINS server in my network. Do I put a permanent entry of Exchange server into the ARP cache of all the client machines? Regards, Chand Deshwal (M.Tech CS&E, MCSE, CCNA) Network Manager Kampsax India Ltd. (ISO 9002 company) Gurgaon - India Ph. 91 6348259-62 E-mail: chand@xxxxxxxxxxxxxxxxx <mailto:chand@xxxxxxxxxxxxxxxxx> Web: http://www.kampsaxindia.com -----Original Message----- From: Andy Ching [mailto:AndyChing@xxxxxxxxxxxxx] Sent: Wednesday, March 20, 2002 11:06 AM To: [ExchangeList] Subject: RE: Exchange Service Pack - 4 http://www.MSExchange.org/ This is a multi-part message in MIME format.