SMTP Status Codes

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1xx Informational

101 The server is unable to connect

111 Connection refused or inability to open an SMTP stream

2xx Success

200 System status message or help reply

214 A response to the HELP command

220 The server is ready

221 The server is closing its transmission channel

250 Requested mail action okay completed

251 User not local will forward

252 Cannot verify the user, but it will try to deliver the message anyway

3xx Redirection

354 Start mail input

4xx Persistent transient failure

420 Timeout connection problem

421 Service is unavailable due to a connection problem

422 The recipient’s mailbox has exceeded its storage limit

431 Not enough space on the disk

432 Recipient’s incoming mail queue has been stopped

441 The recipient’s server is not responding

442 The connection was dropped during the transmission

446 The maximum hop count was exceeded for the message

447 Message timed out because of issues concerning the incoming server

449 Routing error

450 User’s mailbox is unavailable

451 Aborted – Local error in processing

452 Too many emails sent or too many recipients

471 An error of your mail server

5xx Permanent errors

500 Syntax error

501 Syntax error in parameters or arguments

503 Bad sequence of commands, or requires authentication

504 Command parameter is not implemented

510 Bad email address

511 Bad email address

512 Host server for the recipient’s domain name cannot be found in DNS

513 Address type is incorrect

523 Size of your mail exceeds the server limits

530 Authentication problem

541 The recipient address rejected your message

550 Non-existent email address

551 User not local or invalid address – relay denied

552 Exceeded storage allocation

553 Mailbox name invalid

554 Transaction has failed