Email bouncing from 451 error

Posted on 2011-03-15
Last Modified: 2014-02-20
When an outside sender sends an email using a distribution group that has a user inside our organization as a recipient then the email is bounced just for our user back to the sender.  We use MX Logic as our hosted email, I have checked the logs on MX Logic and it shows the following error: "Detail: first attempt failure: 451 unknown error writing data to backend for message"
Here is the part I don't understand, when the email is sent directly to our user it goes through fine. I've checked the SMTP logs (turned on logging) and they do not show the message being blocked.  Just the message that is going through.  I've contacted MX Logic and they said that our Exchange server is blocking the message but I don't see any record of it using message tracking nor going through the SMTP logs.  Anyone have any other suggestions for trying to track down why this message will not go through?

Server 2003 R2 x64
Exchange 2007 SP2
Question by:ddonalson
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Expert Comment

ID: 35142933
Make sure the Group is set to accept permission for Anonymous users.

Find the Group in ADUC and right click and check the exchange settings

Author Comment

ID: 35142974
This distribution group is outside our organization and cannot be controlled.

The recipient is unable to receive the email when it is sent using a distribution but when the sender sends it directly to our user it works fine.
Email address is correct on both emails and it is the exact same email that is sent using both ways (group and directly).

Expert Comment

ID: 35143653
Clue: "outside sender sends an email using a distribution group", the distribution group exists at the outside senders' mail system. Seems neglected to ask that you get an Non-Delivery Report or NDR from the outside sender. I would suppose that your Internet mx record points to MX Logic, your hosted email. at one time it pointed to your original server. The sender's Distribution list has the direct mail address cached as part of the Distribution list. (Their mail client software may also be caching.)  I've commonly seen this on senders that use Notes/Domino. Since they probably won't bother fixing this, creating a user stub on your exchange server to forward email to your hosting provider. (as long as your email can still get to your Exchange server, when that is disconnected from the internet ...)
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Author Comment

ID: 35151513
Our hosted service (MX Logic) has been in use since 2009 and I am also seeing the email go to the hosted service and sit there until a NDR is sent back to the sender.  The NDR that I'm seeing is being reported for the MX Logic service through there logs.  

Another thing I tried doing was using the no fixup command on the asa but that had no effect.

Expert Comment

ID: 35169760
"I've checked the SMTP logs (turned on logging) and they do not show the message being blocked.  Just the message that is going through.  I've contacted MX Logic and they said that our Exchange server is blocking the message but I don't see any record of it using message tracking nor going through the SMTP logs." Why would you think the SMTP logs of MX Logic would be useful? Why didn't you check your own Exchange Server logs?

Look at the NDR carefully or better yet post it. You need a complete NDR from the actual sender at the problem company, since distribution lists from others work. See useful error codes you are ignoring by not getting an actual NDR. Error 451 seems to indicate that a path to the recipient was available but busy, Exchange and other ESMTP servers will attempt several times to redeliver later, hence the delayed NDR.

SMTP is outgoing messages from server to server. MXLogic's server will query your server to deliver if the user is in your domain and the alias does not exist on their server.  The last message returning the NDR from their server will be a refusal from your server.  

Accepted Solution

ddonalson earned 0 total points
ID: 35186827
I am waiting for confirmation from the end user but I did two things.

1.  Added the sender to the white list (Even though I contacted the hosted email and they said our email server was blocking it).

2.  Also, issued the no fixup smtp command on the ASA.

So far, the user reported 1 email coming through.  Hopefully this is resolved.

Author Closing Comment

ID: 35360903
other solutions did not help.  Solution was resolved by following the listed steps.

Expert Comment

ID: 39873593
I will second that making the ASA adjustment resolved this problem for me.

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