Exchange 2010 - emails cant be delivered to some domains?

[sidewinder]

Up until the summer here we had Exchange 2003. I rebuilt the network over summer and now have Exchange 2010. It is setup to forward mail to a smarthost (Inty MailDefender). Had no real problems until now.

 

One teacher has reported that he has had quite a few undeliverables when he has emailed external addresses. I haven't come across this problem myself, and he is the only one to complain.

 

These are the 2 he has forwarded to me so far:

They are:

 

550 No [email protected]\, try [email protected]"> #SMTP# (I thought this would be because the address doesn't exist - but it works ok from his home email)

 

550 5.1.1 : Recipient address rejected: User unknown in relay recipient table> #SMTP#

 

 

One thing I have noticed is that in both the following is in the text:

 

"Received: from ourmailserver.ourdomain.local (unknown [Our external IP address is here])"

 

Could that be part of the problem? Our mail server is presenting itself with its internal DNS name but our external IP address, which obviously don't resolve.

We don't really have an external DNS name (such as mail.ourschool.org) that resolves to the external address, I assume because its always been sent through Maildefender.

 

I did try to duplicate every setting from our old server, but as that was 2003 and this is 2010, a lot has changed so I could have missed something?

[sukh]

Can you pos the complete NDR or PM me.

 

Can you send to this receipient use OWA (internally?

Create a new Outlook profile and test.

Can other internal users send to this domain and/or other recipients at this domain?

[sidewinder]

Hi Sukh, just pm'd you one of them

 

Will try OWA later. Contarary to what I said in the PM, I have got the same NDR's back after emailing both addresses. So it would appear it doesn't just affect one user