How do I interpret the delivery failure message that I have received?

A bounce message/delivery failure message contains information about the message delivery problem that you've encountered. How the information is formatted and stated in a bounce message will vary depending on the mail server sending the message back to you. Some messages contain technical terms while some contain paragraphs describing that you probably just misspelled your recipient's e-mail address.

A Sample bounce message:

    You'll see this information when you display the full message headers of the bounce message that you've received. The most important information here is the Diagnostic-Code.

Delivery to the following recipients failed.

       *** Email address is removed for privacy ***

Reporting-MTA: dns;BAY0-OMC3-S10.bay0.outlook.com

Received-From-MTA: dns;BAY121-W55

Arrival-Date: Tue, 10 Jun 2008 14:21:03 -0700

Final-Recipient: rfc822; *** Email address is removed for privacy ***

Action: failed

Status: 5.5.0

Diagnostic-Code: smtp;550 *** Email address is removed for privacy *** unknown user account

Common bounce messages:

1. Mailbox Not Found, Invalid mailbox, User unknown:

    The e-mail address that you're sending to doesn't exist. Check your recipient's e-mail address. Either you have misspelled it or it's an old e-mail address that's no longer in use. You can double-check it with your recipient.

2. Mailbox unavailable:

    9 times out of 10, this is the same as "mailbox not found". That other 10% of the time it could mean that there's a problem with your recipients account. Check to make sure that you have the e-mail address correct, wait a while and try again. If it still bounces, try contacting the recipient some other way.

3. Mailbox full or Quote Exceeded:

    As what the error states, your recipient have too much message and the server hosting it isn't accepting any more. Contact your recipient through other means and advise him/her to clean up his/her mailbox.

4. Host unknown, Domain Lookup Failed:

    This means that the mail server you're attempting to send to (the "hotmail.com" part in the example above) doesn't exist. Make sure you type your recipient's e-mail address correctly. Another reason is when an ISP changes their name (like when "attbi.com" changed their name to "comcast.com". If you try to send a message to an old "attbi.com" e-mail address, you might get this message in return.).

5. Message too large:

    The message that you are trying to send is too large or exceeds your recipient's mailbox limit.  This usually happens when the host of your recipient has a limit on the size of messages that they can receive. Reduce the size of your message. If you are trying to send a file, you may need to compress it using a file compression program, like WinZip. 

6. Temporary Errors (no adequate servers, Connection Timed Out, Resources temporarily unavailable, Out of memory):

    There's a problem with the mail server that you probably don't have any control over. As stated, these are temporary errors and should resolve themselves over time. Check the bounce message carefully because the mail server mentioned in it may continue to try to deliver your message without any action required on your part.

7. Blacklist Filters (errors that included the word "blocked" or "listed in" and references to sites that have things like "spamcop", "dynablock", "blackhole", "spamhaus" etc):

    This means that your message is intentionally blocked because the receiving system thinks that the mail server you're using is a source of spam. Contact the support team of recipient's e-mail provider and request to have your account or domain unblocked.