What are the common SMTP response codes?

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If at any stage in an SMTP transaction there is an error, it will have a unique code assigned to it so the user can hopefully determine why it has happened.

However the response codes are not always errors,
SMTP will also output a success code.

The first digit of the response denotes whether it is good, incomplete or simply bad.

2 – Success reported
4 – Temporary failure
5 – Permanent failure


Here are a list of known codes:

Response code Description
211 System status or system help reply
214 Help message
220 service ready
221 service closing transmission channel
250 Requested mail action okay, completed
283 The Gordano server is configured so that messages aren’t being saved. The FROM and TO address are taken from the e-mail message headers
354 Start mail input; end with
421 service not available, closing transmission channel
450 Requested action not taken; mailbox unavilable or busy
451 Requested action aborted, local error in processing
452 Requested action not taken, insufficient system storage
500 Syntax error, command unrecognized. Also command line too long
501 Syntax error in paramaters or arguements
502 Command not implemented
503 Bad sequence of commands
504 Command parameters not implemented
550 Action not taken. Mailbox unavailable. Not found, not accessible
551 User not local, please try
552 Exceeded storage allocation
553 Mailbox name not allowed. Mailbox syntax may be incorrect
554 Transaction failed

See Also:

Keywords:SMTP response code theory error

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