Background: We have an SBS2003 server configured to send and receive email. All has been working fine until about 2-3 months ago when my users stopped receiving email from a specific domain. Additional Info: The way that we are setup is as follows. A third party gets our email, performs the neccessary spam checks and forwards them to our server. There is no A/V or any additional spam filtering occuring on our server. All PTR/MX/A records are correct as far as I know. PTR from my server IP goes to mail.myservercom. A record and MX recordgoes to filter IP. The sender gets the following NDR Could not deliver the message in the time limit specified. Please retry or contact your administrator. <sender.server.LOCAL #4.4.7> Is there anything that I can check or do on my side to fix this? Thanks

Please get the full NDR from them, it could be an issue on their side, maybe they have a specific connector with incorrect smarthost or DNS going to your domain. Could be many reasons. 1. Get the full NDR and post back. 2. You can check your SMTP logs and message tracking, prob won't show anything, I thinking their mail server never even hit your providers mail server. 3. You can request from your third party mail provider to check their smtp logs. I would start with number 1 to eliminate if its an issue with the sending company first, that's my hunch. James Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com

By full NDR you mean with the internet headers on it? If so I can provide that as soon as I head back to the office.

Actually I wouldn't worry about posting the NDR or the headers, the NDR you posted is just their mail server saying message to domain timed out, so there will be no further information from the NDR nor the headers. I would start with the suggestions I mentioned. James Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com

I started the smtp logging and I'll let you know how it goes.

hi, any update? thanks, CastinLu TechNet Community Support Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com

I have at least 48 hours of SMTP log files. What should I be looking for? I assume that I should be looking for any attempts to receive email from the "problematic" domain correct?

That's correct just narrow focus on the time they attempted to send, sender\recipient and subject. If you don't see any entries (which I"m expecting) than they never sent it. It would likely be an issue on their end, maybe they have a bad DNS\connector for your domain and thus could never find your mail server in the first place.James Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com

As you were expecting, there was no entry in the log files from them. I have asked both the sender and the third party filter to check, if possible, their SMTP logs so as to see where the email stops. If there is a problem with the senders DNS\connector how can I assist them to fix it? Thanks

hi, >>>If there is a problem with the senders DNS\connector how can I assist them to fix it? If their send connector has problem, i think you can ask them to create new send connnector which is used to send message to your exchange, set your hub as the smart host and set your domian as the address space. So each message sent to your exchange will pass through the send connector and delivered by their and your hub server. hope can help you thanks, CastinLu TechNet Community Support Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com

hi, Any update? thanks, CastinLu TechNet Community Support Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contacttnmff@microsoft.com

I'm having some issues getting in touch with their IT department in order to try what you have recommended. As soon as I get in touch with them I'll let you know how it goes.

hi, If you will, please first mark as answer. If your issue still come back, you can open a new post or reopen the thread. thanks, CastinLu TechNet Community Support Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contacttnmff@microsoft.com

Ok I have some new information. Apparently the problem is not just with receiving from the "problematic" domain but also sending to it. I've asked my users to send some test email over the next few hours so that I can have a look at the log files to see if there is any indication of where the fault is.