One of our branch offices is configured with a single W2K3 Standard Edition server, fully patched, configured as a domain controller with Exchange 2003 installed. It's not under a huge load - it supports 5 users - and has been functioning just fine until about 3 weeks ago. The issue now is that the SMTP service will intermittently stop accepting connections from our external mail server.(it is configured to only accept connections from this server). If I suspect this has happened, I will attempt a telnet connection from the external server to port 25 on the branch server - if it connects, then fine otherwise the connection attempt will time out. If I log in via RDP to the branch server & re-start the SMTP service it will start accepting connections again. (although i'll lose my RDP connection) I have tried: - updating all server software - updating NIC drivers (an old Intel PRO/100) - Checked the SenderID setting on the virtual SMTP server - it's turned off - cleared a checkbox on the driver properties page that allowed the computer to power down the adaptor to save power - Disabled chimney-ing as described in: http://blogs.technet.com/b/exchange/archive/2007/07/18/3403490.aspx (used the netsh method) - turning up all transport-related Exchange logging options to maximum but have seen nothing As you may guess, I'm at my wit's end and what little of my hair remains is disappearing fast. I'd appreciate any bits of wisdom that anyone out thee can provide. Thanks, don

Hi Its not recommended to run Exchange on DC, please move your Exchange server to other member server.