Hi, I've been playing a bit with Exchange 2007 (see end of post for config specs), trying to see how far it can go. I was mainly aiming at the maximum concurrent SMTP connections it can handle. I first removed the 5k limitations using the following command in the Exchange Management Console : Set - ReceiveConnector - Identity MyReceiveConnector - MaxInboundConnection unlimited And then I started shooting SMTP connections at a 1k per second rate. The connections are just OPEN command, so it remains inactive until the ConnectionInactivityTimeout is reached and then farewell. That's it for the test set up. The result is a nice and clean 144, 000 concurrent connections. (Reached several times, exactly the same value) I'd like to have your opinion on what may cause this specific value. I've noticed a 98% usage of memory, nothing special on network or CPU activity. Thank you for your time. Config: Exchange 2007 v08.01.0240.006 Windows Server 2008 SP1 64 bit 2 Xeon E5405 (quad core, 2ghz/core) 4GB RAM 1Gb ethernet

This does not seem to be a limit of Exchange 2007. It may be caused by underlying API or service Exchange uses although it is difficult to say what without looking at stack trace.Bhargav Shukla - MSFT | Exchange Server 2007 TechCenter - http://technet.microsoft.com/en-us/library/bb124558.aspx | Exchange Server 2003 TechCenter - http://technet.microsoft.com/en-us/library/bb123872(EXCHG.65).aspx | Microsoft Exchange Team Blog - http://msexchangeteam.com/default.aspx