Exchange 2010 NDR for Messages over Size Limit?
Good afternoon, We recently had a consulting company upgrade us from an Exchange 2003 to Exchange 2010. When people (clients, customers, vendors, etc) from outside of our email domain send messages to us with attachments that exceed our maximum size limit on the HT | Transport Settings (20 MB), they don't get a NDR of some sort that tells them their message were not delivered. This results in frustrated clients do to the communication gap. They think their email was delivered fine since they didn't get anything bouncing back. Our consulting company said that this is the way that Exchange 2010 works. This seems odd to me. If 2003 had some sort of over size limit NDR, why not 2010? Can someone tell me if this is the way Exchange 2010 actually functions or not?
April 24th, 2012 3:08pm

Hi You do get over limit NDRs, there is an example of one if this help article: http://technet.microsoft.com/en-us/library/bb232118.aspx What is the NDR setting for the default remote domain (Org Config -> Hub Transport -> Remote Domains -> Default -> Message Format) is Allow NDRs ticked? Cheers, Steve
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April 24th, 2012 3:41pm

Can you describe your inbound SMTP architecture? Does Exchange accept the messages directly from the internet or is there a SMTP gateway in between that accepts mail for you? The issue here is that if a message is oversized, then Exchange will never accept the message - thus no NDR is generated by Exchange - because its actually the sending SMTP gateway that is then responsible for the generating the NDR back to the original sender. Can you post the exact NDR senders get when the message is rejected?
April 24th, 2012 4:19pm

Yes, "Allow non-delivery reports" is checked as well as "Allow automatic replies", "Allow automatic forward", "allow delivery reports", and "Dispaly sender's name on messages". It was one of the first things I checked but no luck :-)
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April 24th, 2012 4:47pm

Sure thing. Here is what we have going on... We have one location that our mail is delivered to with one MX record for this site. When inbound mail hits our firewall, it directs it to an in-house spam appliance (Sonicwall) From there, the Sonicwall does the normal anti-spammy things to it to check for good/bad messages and forwards it for delivery to our internal exchange server in the same site and subnet as the Sonicwall. I cannot post the NDR that senders get simply because they never get one. And that's the problem. They never get one even though the message was never delivered to the recipient so they think it's delivered but it is not so they get mad because they think we're ignoring them.
April 24th, 2012 4:53pm

Sure thing. Here is what we have going on... We have one location that our mail is delivered to with one MX record for this site. When inbound mail hits our firewall, it directs it to an in-house spam appliance (Sonicwall) From there, the Sonicwall does the normal anti-spammy things to it to check for good/bad messages and forwards it for delivery to our internal exchange server in the same site and subnet as the Sonicwall. I cannot post the NDR that senders get simply because they never get one. And that's the problem. They never get one even though the message was never delivered to the recipient so they think it's delivered but it is not so they get mad because they think we're ignoring them. Sorry, What I was thinking didnt make it to the keyboard. What I meant was, in those occasions when NDRs are sent, what do they say? I assume when sending to an invalid recipient, senders get a NDR or no? Now for the other piece, is the 20MB limit set on the SonicWall? Because that is where it should rejected and the message should never even make it to the Exchange servers.
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April 24th, 2012 5:17pm

Sorry, What I was thinking didnt make it to the keyboard. What I meant was, in those occasions when NDRs are sent, what do they say? I assume when sending to an invalid recipient, senders get a NDR or no? Now for the other piece, is the 20MB limit set on the SonicWall? Because that is where it should rejected and the message should never even make it to the Exchange servers. Correct, when sending to an invalid recipient, the sender do get an NDR. Yes, the 20 MB is set on the SonicWall and the Exchange Server.
April 24th, 2012 7:42pm

Sorry, What I was thinking didnt make it to the keyboard. What I meant was, in those occasions when NDRs are sent, what do they say? I assume when sending to an invalid recipient, senders get a NDR or no? Now for the other piece, is the 20MB limit set on the SonicWall? Because that is where it should rejected and the message should never even make it to the Exchange servers. Correct, when sending to an invalid recipient, the sender do get an NDR. Yes, the 20 MB is set on the SonicWall and the Exchange Server. Ok, then I would start with the SonicWall. Can you send an oversized message to your org from the outside as a test? I would enable SMTP logging on the Sonic Wall and then send the message. If you dont get a NDR, check the SMTP logs on the SonicWall and see what it reveals.
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April 24th, 2012 8:16pm

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