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Troubleshooting
Product ConnectXf
Version 3.10
Applies to Administrators
Level Advanced




Message deferred in recipient servers queue with error - Unknown error writing DATA to backend for message

Symptom

  • The sender on Connect Xf is receiving the following warning message periodically from the recipient's mail server
THIS IS A WARNING MESSAGE ONLY
YOU DO NOT NEED TO RESEND YOUR MESSAGE
A temporary error occurred while delivering to the following address(es):
<jude@acmecorp.com>: 451 Unknown error writing DATA to backend for
message (92e39205.59fa9940.131229.00-2491.188427.p02c12m096.mxlogic.net)
I will continue trying to send the message until it is delivered or expires.

Diagnosis

  • Searching for this mail (by sender and recipient) in the /var/log/maillog reveals the following
Aug 14 09:33:07 MailServer qmail: 1344916987.108892 starting delivery 384557: msg 884950 to remote jude@acmecorp.com
Aug 14 09:34:13 Mailserver qmail: 1344917053.168376 delivery 384557: success: 
xx.yy.zz.pp_accepted_message./STARTTLS_proto=TLSv1;_cipher=AS256-SHA;_subject=/C=US/ST=Colorado/L=Denver/
O=MX_Logic,_Inc./OU=Operations/CN=*.mxlogic.net/emailAddress=userid@mxlogic.com;_issuer=/O=Network_Associates/
OU=NAI_Certificate_Services/CN=NAI_SSL_CA_v1;/
Remote_host_said:_250_[INBOUND]_cfdc9205.0.12880.00-2395.16413.p02c12m015.mxlogic.net_QueueSafe/
  • The above logs indicate that the MX Logic server has accepted the mail, but from then on, its unable to deliver to the recipient's mail server.
  • Here is some doumentation related to this issue:
Email bouncing from 451 error
Asked by: ddonalson
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.
http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_26889365.html

Recommendation

To contact the admin of the recipient server and ask them to investigate the issue.