Understanding Undeliverable Emails

Part of proper Business Email Etiquette is to understand the technology you are using and to try and make the effort to get the answers you seek before you rely on someone else to do so for you.

An issue I get asked about quite often is in regard to undeliverable or returned emails that they receive. 9 out of 10 times when an email is returned the sender assumes that the server is broken or not working. That is an incorrect perception and one that is the tip of the iceberg when it comes to why e-mails can be returned to you.

There several common reasons you may receive undeliverable email returns:

• You had a typo in the email address making it incorrect and therefore undeliverable. Conducive to dialing a wrong phone number.
• The person you are emailing actually gave you an incorrect email address (typo) – that happens allot!!
• 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 email program which then does not allow their email account to be cleared as all email is “left on the server”. Until that option is unchecked and all email is downloaded to clear out their email account this will continue to happen. Leave this option unchecked unless you can micromanage it!
• A spammer used a phony email address when sending to you and your autoresponder message could not respond to the bogus email address.
• Someone who has your email address on their system has a virus that is propagating itself to old or non-existent email addresses putting your address in the FROM: field. This causes undeliverable virus generated emails to be returned to you.

Undeliverable error messages are the protocol in place to let you know when messages sent 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 emails, there will always be an “undeliverable reason” and error code at the top of the email as to why the message could not be delivered. If you look closely at the returned message you will see what the problem was. The top of the message will look similar to this:

The original message was received at Thu, 12 Oct 2008 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.rinku.or.jp.: >>> RCPT To: < << 550 ... User unknown 550 ... User unknown

The above reflects that there is no such email address on that system – user unknown.

Here is a listing of the most common error codes you will see in undeliverable emails 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*

*The last error message is the one you’ll see most often due to “forbidden for policy reasons.” This usually indicates an email is spammy or has been identified based on the rejecting servers protocols as having a red flag. Usually large attachments, email formatting and embedded graphics are the culprits.

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

So remember, whenever you get an email that bounces back, there will always be a little message at above the bounced message’s content telling you exactly why the message ha been returned to you. This message is key to you being able to go to the source and get the issue resolved.