RFC 1893 - SMTP Extended Error Messages
For more detail about the RFC1893 : http://www.faqs.org/rfcs/rfc1893.html
The class sub-code provides a broad classification of the status.
The enumerated values the class are defined as:
2.X.X Success
Success specifies that the DSN is reporting a positive delivery
action. Detail sub-codes may provide notification of
transformations required for delivery.
4.X.X Persistent Transient Failure
A persistent transient failure is one in which the message as
sent is valid, but some temporary event prevents the successful
sending of the message. Sending in the future may be successful.
5.X.X Permanent Failure
A permanent failure is one which is not likely to be resolved by
resending the message in the current form. Some change to the
message or the destination must be made for successful delivery.
X.0.X Other or Undefined Status
There is no additional subject information available.
X.1.X Addressing Status
The address status reports on the originator or destination
address. It may include address syntax or validity. These
errors can generally be corrected by the sender and retried.
X.2.X Mailbox Status
Mailbox status indicates that something having to do with the
mailbox has cause this DSN. Mailbox issues are assumed to be
under the general control of the recipient.
X.3.X Mail System Status
Mail system status indicates that something having to do
with the destination system has caused this DSN. System
issues are assumed to be under the general control of the
destination system administrator.
X.4.X Network and Routing Status
The networking or routing codes report status about the
delivery system itself. These system components include any
necessary infrastructure such as directory and routing
services. Network issues are assumed to be under the
control of the destination or intermediate system
administrator.
X.5.X Mail Delivery Protocol Status
The mail delivery protocol status codes report failures
involving the message delivery protocol. These failures
include the full range of problems resulting from
implementation errors or an unreliable connection. Mail
delivery protocol issues may be controlled by many parties
including the originating system, destination system, or
intermediate system administrators.
X.6.X Message Content or Media Status
The message content or media status codes report failures
involving the content of the message. These codes report
failures due to translation, transcoding, or otherwise
unsupported message media. Message content or media issues
are under the control of both the sender and the receiver,
both of whom must support a common set of supported
content-types.
X.7.X Security or Policy Status
The security or policy status codes report failures
involving policies such as per-recipient or per-host
filtering and cryptographic operations. Security and policy
status issues are assumed to be under the control of either
or both the sender and recipient. Both the sender and
recipient must permit the exchange of messages and arrange
the exchange of necessary keys and certificates for
cryptographic operations.
X.0.0 Other undefined Status
Other undefined status is the only undefined error code. It
should be used for all errors for which only the class of the
error is known.
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 mailbox address valid
X.1.6 Mailbox has moved
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.4.0 Other or undefined network or routing status
X.4.1 No answer from host
X.4.2 Bad connection
X.4.3 Routing server failure
X.4.4 Unable to route
X.4.5 Network 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.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
SMTP Protocol - LIST OF REPLY CODES
For more detail about the RFC788 : http://www.faqs.org/rfcs/rfc788.html
=> List of reply codes returned by destination server when source server is sending a command during SMTP session.
211 System status, or system help reply
214 Help message [Information on how to use the receiver or the meaning of a particular non-standard command; this reply is useful only to the human user]
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 [This may be a reply to any command if the service knows it must shut down]
450 Requested mail action not taken: mailbox unavailable [E.g., mailbox busy]
451 Requested action aborted: local error in processing
452 Requested action not taken: insufficient system storage
500 Syntax error, command unrecognized [This may include errors such as command line too long]
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 [E.g., mailbox not found, no access]
551 User not local; please try
552 Requested mail action aborted: exceeded storage allocation
553 Requested action not taken: mailbox name not allowed [E.g., mailbox syntax incorrect]
554 Transaction failed