- 211
- System status, or system help reply
- 214
- Help Message
- 220
- <domain> Service Ready
- 221
- <domain> Service closing transmission channel
- 250
- Requested mail action okay, completed
- 251
- User not local; will forward to <forward-path>
- 252
- Cannt VRFY user, but will accept message and attempt delivery
- 354
- Start mail input; end with <CRLF>.<CRLF>
- 421
- <domain> 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
- 455
- Server unable to accommodate parameters
- 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
- Server does not accept mail
- 550
- Requested action not taken: mailbox unavailable
- 551
- User not local; please try <forward-path>
- 552
- Requested mail action aborted: exceeded storage allocation
- 553
- Requested action not taken: mailbox name not allowed
- 554
- Transaction failed
- 555
- MAIL FROM/RCPT TO parameters not recognized or not implemented
- 556
- Domain does not accept mail
- x.0.0
- Other or Undefined Status
- x.1.0
- Other address status
- x.1.1
- Bad destination mailbox address
- x.1.2
- Bad destination system address
- x.1.3
- Bad destination mailbox address syntax
- x.1.4
- Destination mailbox address ambiguous
- x.1.5
- Destination address valid
- x.1.6
- Destination mailbox has moved, No forwarding address
- x.1.7
- Bad sender's mailbox address syntax
- x.1.8
- Bad sender's system address
- x.2.0
- Other or undefined mailbox status
- x.2.1
- Mailbox disabled, not accepting messages
- x.2.2
- Mailbox full
- x.2.3
- Message length exceeds administrative limit
- x.2.4
- Mailing list expansion problem
- x.3.0
- Other or undefined mail system status
- x.3.1
- Mail system full
- x.3.2
- System not accepting network messages
- x.3.3
- System not capable of selected features
- x.3.4
- Message too big for system
- x.3.5
- System incorrectly configured
- x.4.0
- Other or undefined network or routing status
- x.4.1
- No answer from host
- x.4.2
- Bad connection
- x.4.3
- Directory server failure
- x.4.4
- Unable to route
- x.4.5
- Mail system congestion
- x.4.6
- Routing loop detected
- x.4.7
- Delivery time expired
- x.5.0
- Other or undefined protocol status
- x.5.1
- Invalid command
- x.5.2
- Syntax error
- x.5.3
- Too many recipients
- x.5.4
- Invalid command arguments
- x.5.5
- Wrong protocol version
- x.6.0
- Other or undefined media error
- x.6.1
- Media not supported
- x.6.2
- Conversion required and prohibited
- x.6.3
- Conversion required but not supported
- x.6.4
- Conversion with loss performed
- x.6.5
- Conversion Failed
- x.6.6
- Message content not available
- x.7.0
- Other or undefined security status
- x.7.1
- Delivery not authorized, message refused
- x.7.2
- Mailing list expansion prohibited
- x.7.3
- Security conversion required but not possible
- x.7.4
- Security features not supported
- x.7.5
- Cryptographic failure
- x.7.6
- Cryptographic algorithm not supported
- x.7.7
- Message integrity failure
- x.7.8
- Trust relationship required
- x.7.16
- Future release per-user message quota exceeded
- x.7.17
- Future release system message quota exceeded