SMTP Response Codes
Last updated March 2020
The SMTP response codes and their meanings are shown in the following table.
Note
Prior to versions 3.1 and 2.2.3.47, Momentum would not respond correctly to a 251 (User not local; Will be forwarded) response from a remote server. It put the message in the delayed queue.
| Code | Meaning |
|---|---|
| 211 | System status, or system help reply |
| 214 | Help message |
| 220 | example.com service ready |
| 221 | example.com service closing transmission channel |
| 250 | Requested mail action okay, completed |
| 251 | User not local; will forward to forward-path |
| 354 | Start mail input; end with |
| 421 | example.com service not available, closing transmission channel |
| 450 | Requested mail action not taken: mailbox unavailable |
| 451 | Requested action aborted: error in processing |
| 452 | Requested action not taken: insufficient system storage |
| 500 | Syntax error, command unrecognized |
| 501 | Syntax error in parameters or arguments |
| 502 | Command not implemented |
| 503 | Bad sequence of commands |
| 504 | Command parameter not implemented |
| 550 | Requested action not taken: mailbox unavailable |
| 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 failed |
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