namespace System.Net.Mail { public enum SmtpStatusCode { BadCommandSequence = 503, CannotVerifyUserWillAttemptDelivery = 252, ClientNotPermitted = 454, CommandNotImplemented = 502, CommandParameterNotImplemented = 504, CommandUnrecognized = 500, ExceededStorageAllocation = 552, GeneralFailure = -1, HelpMessage = 214, InsufficientStorage = 452, LocalErrorInProcessing = 451, MailboxBusy = 450, MailboxNameNotAllowed = 553, MailboxUnavailable = 550, MustIssueStartTlsFirst = 530, Ok = 250, ServiceClosingTransmissionChannel = 221, ServiceNotAvailable = 421, ServiceReady = 220, StartMailInput = 354, SyntaxError = 501, SystemStatus = 211, TransactionFailed = 554, UserNotLocalTryAlternatePath = 551, UserNotLocalWillForward = 251 } }