Meaning of Bounce Back Email


I have received a bounce back email. What does it mean?


The reason for the bounce message will usually be located below these lines in the bounce back email you received:

Diagnostic information for administrators:
Generating server:
The reason will appear on this line.


Here is a list of commonly known reasons for bounce back messages. Once you have located the lines above, try and locate it in this list.

#< #5.0.0 X-Spam-&-Virus-Firewall; []: Name or service not known> #SMTP#

This means the domain, cannot be resolved via DNS and is therefore unreachable by our mail system. Often this is just due to a mistyped email address, but can also indicate network changes or problems on the recipient's end. In the latter case, the problem can only be resolved by the recipients organization, not WKU.

#< #5.0.0 X-Spam-&-Virus-Firewall; host[] said: 550 5.1.1 User unknown (in reply to RCPT TO command)> #SMTP#

This means that the email address you attempted to send to is unknown by the destination server. You could have mistyped the email address, or used an outdated account that has been deactivated. Double check the spelling of the email address or attempt to contact the intended recipient through other means to obtain the correct address.

Delivery is delayed to these recipients or groups: This message hasn't been delivered yet. Delivery will continue to be attempted. The server will keep trying to deliver this message for the next 1 days, 19 hours and 50 minutes. You'll be notified if the message can't be delivered by that time.

This is due to an issue with the outgoing mail server. A ticket with the bounceback message must be routed to Systems Administration from the ITS Service Desk. #554 rejecting banned content ##

This means the spamcontrol server has identified part of the message as containing spam. Many times the spam content is not visible and can indicate the sender's computer has an infection of some kind. To determine if such is the case, a ticket should be routed to Systems Administration from the ITS Service Desk.

#550 5.3.4 ROUTING.SizeLimit; message size exceeds fixed maximum size for route ##

This means the message exceeds the size limit restrictions. Ensure that your attachments are below the size limit for Faculty/Staff email and for TopperMail.


Service Desk Consultants Only

  1. Gather the bounceback message from the client.
  2. Fill out ticket Software and Enterprise Systems > Exchange > Question, Problem, or Email Client Settings with the bounce back message pasted into the ticket.
  3. Route the ticket to Systems Administration.


Article ID: 911
Mon 11/17/14 11:19 AM
Fri 2/12/21 2:15 PM