SMTP Inbound Timout Exchange 2003 - Small Business Server

Config is:

SBS2003, single nic, behind a LINKSYS BEFSR41 V4 router doing PPoE to Qwest DSL.  The linksys is behind a Cisco 678 in bridge mode.

Some email is not being received by my SBS2003 server.  It is from a few specific domains that I've identified so far.   Not all the hotmail/msn is timing out, only from certain servers.  All of the is timing out.  

My server doesn't spit back an NDR of any kind, but eventually the sending server reports back to the sender that it can't deliver, a 4.4.7 code similar to:

Action: failed
Status: 4.4.7
Remote-MTA: DNS;
Diagnostic-Code: SMTP; 451 4.4.1 reply: read error from

I've searched extensively via google for topics like this and have found several, but none with a consistent solution.  I've tried many of them already, including:

- Changing MTU settings from 1492 to 1400.
- Changing NIC from auto-detect to 100 MBps Full Duplex.
- Updating firmware on LINKSYS router
- Changing timeout on SMTP virt to 5 mins from 10.

SMTPSVC log snippet:

2006-04-18 16:05:08 SMTPSVC1 SERVER 0 EHLO - 250 0 222 31 0 SMTP - - - -
2006-04-18 16:05:08 SMTPSVC1 SERVER 0 MAIL - +FROM:<> 250 0 119 117 0 SMTP - - - -
2006-04-18 16:05:08 SMTPSVC1 SERVER 0 RCPT - +TO:<> 250 0 47 44 0 SMTP - - - -
2006-04-18 16:06:14 SMTPSVC1 SERVER 0 EHLO - 250 0 223 20 0 SMTP - - - -
2006-04-18 16:06:14 SMTPSVC1 SERVER 0 MAIL - +From:<> 250 0 27 22 0 SMTP - - - -
2006-04-18 16:06:14 SMTPSVC1 SERVER 0 RCPT - +To:<> 250 0 43 40 0 SMTP - - - -
2006-04-18 16:09:34 SMTPSVC1 SERVER 0 TIMEOUT - 121 1152226112 84 4 266109 SMTP - - - -
2006-04-18 16:09:34 SMTPSVC1 SERVER 0 QUIT - 240 266250 84 4 266125 SMTP - - - -
2006-04-18 16:11:04 SMTPSVC1 SERVER 0 TIMEOUT - 121 3052993041 84 4 290438 SMTP - - - -
2006-04-18 16:11:04 SMTPSVC1 SERVER 0 QUIT - 240 290610 84 4 290438 SMTP - - - -

The existing DSL connection is slated to be replaced with a fractional T1 at the end of April so I'm not eager to start replacing lots of hardware.   I'm contemplating adding a secondary MX entry on a 2K server that I control to act as a relay.

Any ideas of how to solve the problem as it exists?
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What have you got scanning the SMTP traffic?
Antivirus, antispam? Those are the common reasons for delivery failure.

nummagumma2Author Commented:
SAV for MS Exchange.  SAV 10 on the server.  GFI Mail Essentials.

With every one of those services off the problem still happens.
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please make sure port 25 open
and do you have ISA?anty spam protector?


Disabling the product doesn't help if they are causing the problem. Due to the way that these products integrate in to the server, the only way to ensure they aren't interfering is to remove them.

Also, test your domain here: 
Do a netstat on the server and see if it is in fact listening on port 25 or break out port query: 


nummagumma2Author Commented:
Replacing the linksys router with a new one (the one I replaced had been in service 2 months) solved the problem.
nummagumma2Author Commented:
mcsa2003, your comments didn't appear to apply since the vast majority of mail was flowing just fine.
Closed, 500 points refunded.
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