Undeliverable or Returned E-mails

I get asked about this all the time from my clients, so I thought I would share with you today information on undeliverable or returned e-mails. The several common reasons you may receive undeliverable e-mail returns:

• You had a typo in the e-mail address making it incorrect and therefore undeliverable. Conducive to dialing an wrong phone number.


• The person you are e-mailing actually gave you an incorrect e-mail address (typo) - that happens a lot!!


• Their inbox is filled to capacity due to large attachments or not logging in for a while. Another cause is they have "leave mail on server" checked in their e-mail program which then does not allow their e-mail account to be cleared as all e-mail is "left on the server". Until that option is unchecked and all e-mail is downloaded to clear out their e-mail account this will continue to happen. Leave this option unchecked unless you can micro-manage it!


• A spammer used a phony e-mail address when sending to you and your autoresponder message could not respond to the bogus e-mail address.


• Someone who has your e-mail address on their system has a virus that is propagating itself to old or non-existent e-mail addresses putting your address in the FROM: field. This causes undeliverable virus generated e-mails to be return to you.

Undeliverable error messages are the protocol in place to let you know when messages do not (for many different reasons) make it to the intended recipient. You want to become familiar with how these messages relay exactly what the problem is.

With all returned e-mails, there will always be an "undeliverable reason" at the top of the e-mail as to why the message could not be delivered. Many of you have noticed as of late the rash of Undeliverable Messages being returned by your ISPs due to viruses.

If you look closely at the returned message you will see what the problem was - they look similar to this:

The original message was received at Thu, 12 Jun 2003 18:45:05 -0500 (EST) from tiberius-t.isp.net [207.69.232.22]
----- The following addresses had permanent fatal errors -----
----- Transcript of session follows -----
... while talking to mx.server.name.here.:
>>> RCPT To: <<< 550 ... User unknown 550 ... User unknown

The above reflects that there is no such e-mail address on that system - user unknown.

Here is a listing of the most common error codes you will see in undeliverable e-mails and what they mean:

=> 251 User not local; will forward to 421 Service not available, closing transmission channel

=> 450 Requested mail action not taken: mailbox unavailable (E.g., mailbox busy)

=> 451 Requested action aborted: local error in processing

=> 452 Requested action not taken: insufficient system storage

=> 500 Syntax error, command unrecognized

=> 501 Syntax error in parameters or arguments

=> 502 Command not implemented

=> 503 Bad sequence of commands

=> 504 Command parameter not implemented

=> 550 Requested action not taken: mailbox unavailable (E.g., mailbox not found, no access)

=> 551 User not local

=> 552 Requested mail action aborted: exceeded storage allocation (mailbox filled)

=> 553 Requested action not taken: mailbox name not allowed (E.g., mailbox syntax incorrect)

=> 554 Transaction failed

These messages vary depending on the systems involved in the delivery of the e-mail. And, you will always see the e-mail that could not be delivered below the error message to see if it is in fact an e-mail you sent, your autoresponder or a virus generated e-mail that you did not send.

HTH!