SMTP Status Codes
Basic status code
| Code | Desciption |
|---|---|
2xx | positive comletion – the requested action has been successfully completed |
3xx | posttive intermediate – the command has been accepted, but the requested aaction is being held in abeyance, pending receipt of further information |
4xx | transient negative completion – the command was not accepted and the requested action did not occure, error condition is temporary and action may be requested again |
5xx | permanent negative completion – the command was not accepted and the requested aciton did not occure, SMTP client SHOULD NOT repeat the exact request (in same sequence) |
x0x | syntax - these replies refer to syntax errors, syntactically correct commands that do not fit any functional category, and unimplemented or superfluous commands |
x1x | information - these are replies to requests for information |
x2x | connections - these are replies referring to the transmission channel |
x3x | unspecified |
x4x | unspecified |
x5x | mail system - these replies indicate the status of the receiver mail system |
Enhanced status code
| Code | Desciption |
|---|---|
2.x.x | success - report of a positive delivery action |
4.x.x | persistent Transient Failure - message as sent is valid, but persistence of some temporary conditions has caused abandonment or delay |
5.x.x | permanent Failure - not likely to be resolved by resending the message in current form |
x.0.x | other or undefined status |
x.1.x | addressing status |
x.2.x | mailbox status |
x.3.x | mail system status |
x.4.x | network and routing status |
x.5.x | mail delivery protocol status |
x.6.x | message content or media status |
x.7.x | security or policy status |
2xx Positive completion
| Code | Desciption |
|---|---|
211 | System status, or system help reply |
214 | Help message (A response to the HELP command) |
220 | |
221 | |
221 | 2.0.0 Goodbye |
235 | 2.7.0 Authentication succeeded |
240 | QUIT |
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 Positive intermediate
| Code | Desciption |
|---|---|
334 | (Server challenge - the text part contains the Base64-encoded challenge) |
354 | Start mail input |
4xx Transient negative completion
“Transient Negative” means the error condition is temporary, and the action may be requested again. The sender should return to the beginning of the command sequence (if any).
The accurate meaning of “transient” needs to be agreed upon between the two different sites (receiver- and sender-SMTP agents) must agree on the interpretation. Each reply in this category might have a different time value, but the SMTP client SHOULD try again.
| Code | Desciption |
|---|---|
421 | Service not available, closing transmission channel (This may be a reply to any command if the service knows it must shut down) |
432 4.7.12 | A password transition is needed [3] |
450 | Requested mail action not taken: mailbox unavailable (e.g., mailbox busy or temporarily blocked for policy reasons) |
451 | Requested action aborted: local error in processing |
451 4.4.1` | IMAP server unavailable [4] |
452 | Requested action not taken: insufficient system storage |
454 4.7.0` | Temporary authentication failure [3] |
455 | Server unable to accommodate parameters |
5xx Permanent negative completion
The SMTP client SHOULD NOT repeat the exact request (in the same sequence). Even some “permanent” error conditions can be corrected, so the human user may want to direct the SMTP client to reinitiate the command sequence by direct action at some point in the future.
| Code | Desciption |
|---|---|
500 Syntax error, command unrecognized (This may include errors such as command line too long) | |
500 5.5.6 Authentication Exchange line is too long | |
501 Syntax error in parameters or arguments | |
501 5.5.2 Cannot Base64-decode Client responses | |
501 5.7.0 Client initiated Authentication Exchange (only when the SASL mechanism specified that client does not begin the authentication exchange) | |
502 Command not implemented | |
503 Bad sequence of commands | |
504 Command parameter is not implemented | |
504 5.5.4 Unrecognized authentication type | |
521 Server does not accept mail | |
523 Encryption Needed | |
530 5.7.0 Authentication required | |
534 5.7.9 Authentication mechanism is too weak | |
535 5.7.8 Authentication credentials invalid | |
538 5.7.11 Encryption required for requested authentication mechanism | |
550 Requested action not taken: mailbox unavailable (e.g., mailbox not found, no access, or command rejected for policy reasons) | |
551 User not local; please try | |
552 Requested mail action aborted: exceeded storage allocation | |
553 Requested action not taken: mailbox name not allowed | |
554 Transaction has failed (Or, in the case of a connection-opening response, “No SMTP service here”) | |
554 5.3.4 Message too big for system | |
556 Domain does not accept mail |