The subject of SMTP errors massages recently came up when a new client called us to ask for more information on what these mean and how they affect their delivery.
Upon taking the time to explain these to our client, I thought that perhaps more individuals and organizations might have similar questions and the reason for this post.
Upon sending email campaigns to those who subscribed to your email newsletter your email delivery manager will receive SMTP error codes. These error messages are something that can actually help your email marketing reputation if steps are taken to resolve the concerns.
The reason for these errors messages is in the error code itself and is due to an issue that exists between the email server that your organization manages and the email server that email is being sent to which is unable to deliver it.
Many industry veterans in email marketing also described SMTP error code replies as bounce messages. The reason is because the original email message that was sent out never got to its destination and came back (bounced) to you with an SMTP error code.
The bounces messages are known as Delivery Status Notification (DSN) message, Non-Delivery Report/Receipt (NDR) or Non-Delivery Notification (NDN).
Below are the SMTP errors codes that your email marketing delivery manager will see on a regular basis as well as a link to view more details about these error messages.
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 VRFYed, but the server accepts the message and attempts delivery.
354 – Start message input and end with. This indicates that the server is ready to accept the message itself
421 – The service is not available and the connection will be closed.
450 – The requested command failed because the user’s mailbox was unavailable (such as being full). Try again later.
451 – The command has been aborted due to a server error. (on their side)
452 – The command has been aborted because the server has insufficient system storage.
500 – The server could not recognize the command due to a syntax error.
501 – A syntax error was encountered in command arguments.
502 – This command is not implemented.
503 – The server has encountered a bad sequence of commands.
504 – A command parameter is not implemented.
550 – The requested command failed because the user’s mailbox was unavailable (such as not found)
551 – The recipient is not local to the server.
552 – The action was aborted due to exceeded storage allocation.
553 – The command was aborted because the mailbox name is invalid.
554 – The transaction failed for some unstated reason.