To complete the list of status codes, here are the SMTP Status Codes. These will eventually be replied by your mail server.
 | Code | Description | 
 
 | 200 | (nonstandard success response, see rfc876) | 
 
 | 211 | System status, or system help reply | 
 
 | 214 | Help message | 
 
 | 220 | Service ready | 
 
 | 221 | Service closing transmission channel | 
 
 | 250 | Requested mail action okay, completed | 
 
 | 251 | User not local; will forward to | 
 
 | 354 | Start mail input; end with . | 
 
 | 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 | 
 
 | 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 | 
 
 | 521 | does not accept mail (see rfc1846) | 
 
 | 530 | Access denied (???a Sendmailism) | 
 
 | 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 |