Enum SmtpStatusCode

SmtpStatusCode enumeration

Smtp status codes

public enum SmtpStatusCode


NotDefined0Not defined
GeneralFailure-1General failure
SystemStatus211System status, or system help reply. A SMTP status 211 is a message that gives details about the Mail Server status. In the case of a System Help reply, it is a message to the user requesting help information.
HelpMessage214A help message for a human reader will follow. SMTP 214 is usually provided as a response to the “HELP” command. A user will usually receive this as a displays of information about the mail server and it will most likely be in the form of a link to the FAQ page of THAT particular SMTP software that is running on the mail server. Due to the nature of this error and how the email server responds, it is normally called a reply, as in SMTP Reply 214.
ServiceReady220SMTP Service ready.
ServiceClosingTransmissionChannel221Service closing transmission channel
AuthenticationSucceeded235Authentication Succeeded
Ok250Requested action taken and completed.
UserNotLocalWillForward251The recipient is not local to the server, but the server will accept and forward the message.
CannotVerifyUserWillAttemptDelivery252The recipient cannot be VRFYed, but the server accepts the message and attempts delivery.
Base64Response334Text part containing the [BASE64] encoded string
StartMailInput354Start message input and end with. This indicates that the server is ready to accept the message itself
ServiceNotAvailable421The service is not available and the connection will be closed.
PasswordTransitionNeeded432A password transition is needed
MailboxBusy450The requested command failed because the user’s mailbox was unavailable (such as being full). Try again later.
LocalErrorInProcessing451The command has been aborted due to a server error. (on their side)
InsufficientStorage452The command has been aborted because the server has insufficient system storage.
ClientNotPermitted454Client does not have permission. TLS not available due to temporary reason. Encryption required for requested authentication mechanism.
CommandUnrecognized500The server could not recognize the command due to a syntax error.
SyntaxError501A syntax error was encountered in command arguments.
CommandNotImplemented502This command is not implemented.
CommandNotPermitted503Сommand is not permitted during a mail transaction
UnrecognizedAuthenticationType504Unrecognized authentication type
AuthenticationRequired530The SMTP server requires a secure connection or the client was not authenticated. But sometimes it’s about the recipient’s server blacklisting yours, or an invalid email address.
AuthenticationMechanismIsToWeak534Authentication mechanism is to weak
CredentialsInvalid535Authentication credentials invalid
EncryptionRequiredRequestedMechanism538Encryption required for requested authentication mechanism
MailboxUnavailable550It usually defines a non-existent email address on the remote side.
UserNotLocalTryAlternatePath551“User not local or invalid address – Relay denied”. Meaning, if both your address and the recipient’s are not locally hosted by the server, a relay can be interrupted.
ExceededStorageAllocation552“Requested mail actions aborted – Exceeded storage allocation”: simply put, the recipient’s mailbox has exceeded its limits.
MailboxNameNotAllowed553“Requested action not taken – Mailbox name invalid”. That is, there’s an incorrect email address into the recipients line.
TransactionFailed554This means that the transaction has failed. It’s a permanent error and the server will not try to send the message again.

See Also