How many of us have been sending email for mail years without paying attention to error codes when we receive them? This is easy to do since the normal explanations are most often vague at best.
The post below is from my latest book, "You're Hired . . ." (the Amazon link is below). By knowing these, email senders can experience fewer bounce backs which will result in positive improvements in many areas.
SMTP Error Messages: The Meaning of the Numbers
All robust email users encounter returned messages. When reading the reasons given for the returns, a large percentage of the senders do not understand the explanations. The following list provides brief definitions for the most common email errors. They are important to refer to from a Netiquette point of view, as understanding messages and unavoidable errors can help you to avoid issues such as missing deadlines or similar occurrences.
An email server can be set to reply to any request a client (such as your email program) makes by sending return code. This code consists of three numbers. The first number usually signifies whether the server accepted the command and if it could handle it. There are five possible values defined as follows:
· 0: A syntax error has occurred.
· 1 (informational reply to a request): The server has accepted the command but does not yet take action. A confirmation message is required. Currently, this is not used.
· 2 (a referral to the connection status): The server has completed the task successfully.
· 3 (not generally used): The server has understood the request but requires further information to complete it.
· 4 (not generally used): The server has encountered a temporary failure.
· 5 (refers to the status of the mail system and the mail server): The server has encountered an error.
The second number in this list gives more information about why the email was delivered. The last number is the best recognized and shows more detail of the mail transfer status.
The list below names the following ESMTP (enhanced mail server transfer protocol) server-response codes, as defined in RFC 821 extensions. What they indicate follows:
· 21: A system status message.
· 214: A help message for a human reader follows.
· 220: SMTP service ready.
· 221: Service closing.
· 250: Requested action taken and completed.
· 251: The recipient is not local to the server, but the server will accept and forward the message.
· 252: The recipient cannot be verified, but the server accepts the message and attempts delivery.
· 354: A message input that starts and ends with <CRLF> indicates that the server is ready to accept the message itself (after you have told it who it is from and where you want it to go).
· 421: The service is not available, and the connection will be closed.
· 450: The requested command failed because the user’s mailbox was unavailable—for example, because it was locked. Try again later.
· 451: The command has been aborted due to a server error.
· 452: The command has been aborted because the server has insufficient system storage.
The following error messages are for the email client:
· 500: The server could not recognize the command due to a syntax error.
· 501: A syntax error has been encountered in command arguments.
· 502: Bad gateway.
· 503: The server has encountered a bad sequence of commands.
· 504: A command parameter is not implemented.
· 550: The user’s mailbox is unavailable. Either it no longer exists or the message was blocked for security or policy rules.
· 551: The recipient is not local to the server.
· 552: The action has been aborted due to exceeded storage allocation.
· 553: The command has been aborted because the mailbox name is invalid.
· 554: The transaction failed. There could be many reasons for this, such as an outage or software or network failure.+++++++++++++++++++++++++++++++++++++++++++++=++++++
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In addition to this blog, Netiquette IQ has a website with great assets which are being added to on a regular basis. I have authored the premiere book on Netiquette, “Netiquette IQ - A Comprehensive Guide to Improve, Enhance and Add Power to Your Email". My new book, “You’re Hired! Super Charge Your Email Skills in 60 Minutes. . . And Get That Job!” has just been published and will be followed by a trilogy of books on Netiquette for young people. You can view my profile, reviews of the book and content excerpts at:
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I am the president of Tabula Rosa Systems, a “best of breed” reseller of products for communications, email, network management software, security products and professional services. Also, I am the president of Netiquette IQ. We are currently developing an email IQ rating system, Netiquette IQ, which promotes the fundamentals outlined in my book.
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Netiquette IQ quote for today:
"Teach Your Children To Create Strong Passwords At An Early Age"
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