| 220 |
OK, ready |
| 221 |
Thank you for speaking to me |
| 250 |
OK, done |
| 251 |
OK, user not local, will forward |
| 252 |
OK, cannot VRFY user but will attempt delivery |
| 253 |
OK, messages pending |
| 354 |
Start mail input; end with <CRLF>.<CRLF> |
| 355 |
Octet-offset is the transaction offset |
| 421 |
Service not available, closing transmission channel |
| 450 |
Requested mail action not taken: mailbox unavailable |
| 451 |
Requested action aborted: local error in processing |
| 452 |
Requested action not taken: insufficient system storage |
| 454 |
TLS not available due to temporary reason |
| 458 |
Unable to queue message |
| 459 |
Not allowed: unknown reason |
| 500 |
Command not recognized |
| 501 |
Syntax error, no parameters allowed |
| 502 |
Command not implemented |
| 503 |
Bad sequence of commands |
| 504 |
Command parameter not implemented |
| 521 |
Machine does not accept mail |
| 530 |
Must issue a STARTTLS command first |
| 534 |
Authentication mechanism is too weak |
| 538 |
Encryption required for requested authentication mechanism |
| 550 |
Requested action not taken: mailbox unavailable |
| 551 |
User not local |
| 552 |
Requested mail action aborted: exceeded storage allocation |
| 553 |
Requested action not taken: mailbox name not allowed |
| 554 |
Transaction failed |
| 571 |
Blocked |