It's been awhile, but several months ago, we setup a SBS 2003 with Exchange. We had all kinds of problems with getting mail to go out using SMTP. We tried all kinds of setting changes on the server, with our ISP, etc., etc. The people here on this forum suggested all kinds of things that we could be doing wrong with Exchange and our mail setup, but nothing worked. So, we had to "bite the bullet" and make a paid call to Microsoft support. After several days and hours of phone support, we found that the 2Wire 2700HG-B DSL modem/router supplied by AT&T/SBC has this problem: [URL]http://support.microsoft.com/kb/314825/en-us[/URL] Basically, the router does not respond correctly when it gets too large of a packet to send. Instead of responding back that the packet needs to be broken up into smaller fragments, the transmission times out and the packet gets dropped. For a work-around, we did method 1 in the above article to our SBS, but that didn't work. AT&T was not able to provide any further help, so we couldn't do method 2. Method 3 ultimately fixed the issue. Looking back upon things, other symptoms that had occurred before the implementation of the Exchange server is that we at first were only using the SBS as a DHCP server and gateway. When clients on the network tried to send mail through Outlook and the ISP's SMTP server, we had similar problems where mail was not going out due to the router dropping large packets and not responding back with the appropriate response. Hope this might help other people, especially with this 2Wire modem/router being so popular. Thanks to everyone for their help!
