SMTP reply codes

See rfc2821 for the basic specification of SMTP; see also rfc1123 for important additional information.

See rfc1893 and rfc2034 for information about enhanced status codes.

Check the RFC index for further mail-related RFCs.

This is a list of SMTP error codes and log entries our favourite mail server will use to reply to e-mails that had delivery problems. Note that this replies are only for e-mails that are directed to our Xmail Server, not when Xmail is sending outside (in this case you have the SLOG file and an e-mail response, if enabled in SERVER.TAB, with similar errors from the other mail server, although each one has itís own implementation of this codes).

As a general rule:

421 Service not available, closing transmission channel
The Current Session Reached Smtp Timeout (Command Line: -St timeout)
Xmail cannot create a new session (Reached Command Line: -SX nthreads)
451 Requested action aborted: local error in processing
Xmail cannot create message file or set the related parameters/arguments. Possible causes: Network Error, Hardware Error, Disk Full...
452 Mailbox full
Account over quota (Reached MaxMBSize in USER.TAB) or Insufficient disk space to receive the message. SMTP Log File: RCPT=EFULL
500 Syntax error, command unrecognised
The sender issued a command that Xmail doesnít understand
501 Command not accepted
Negative Response for VRFY command (AllowSmtpVRFY = 0 or not set in SERVER.TAB). SMTP Log File: VRFY=EACCESS
Negative Response for ETRN command (AllowSmtpETRN = 0 or not set in SERVER.TAB).SMTP Log File: ETRN=EACCESS
501 Syntax error in forward path
The sender made a syntax error sending the RCPT TO:<xxx> command. SMTP Log File: RCPT=ESYNTAX
501 Syntax error in return path
Negative Response for MAIL FROM:<> Command if Null Sender is not Allowed (AllowNullSender = 0 or not set in SERVER.TAB). SMTP Log File: SNDR=EEMPTY
The Return Path (MAIL FROM:<xxx>) is malformed or too long. SMTP Log File: SNDR=ESYNTAX
501 Syntax error in parameters or arguments
The sender made a syntax error issuing one of the following commands: VRFY, ETRN, HELO, EHLO or AUTH
503 Bad sequence of commands
The sender issued a bad sequence for one of the following commands: HELO, EHLO, MAIL FROM, RCPT TO, DATA or AUTH
503 Authentication failed
Wrong User or Password. SMTP Log File: AUTH=EFAIL:TYPE Ö (PLAIN, LOGIN, CRAM-MD5, EXTRN)
504 Unknown authentication
Xmail doesnít understand the authentication method specified by the sender
504 You are registered as spammer
Sender IP address is listed in SPAM-ADDRESS.TAB file. SMTP Log File: SNDR=ESPAM
505 Your domain has not DNS/MX entries
Negative Response if no SMTP server is found after issuing MAIL FROM:<xxx> command (when CheckMailerDomain = 1 is set in SERVER.TAB). SMTP Log File: SNDR=ENODNS
550 Relay denied
The Recipient Domain (RCPT TO:<xxx>) is not in Xmailís DOMAINS.TAB (or the sender IP address is not listed in SMTPRELAY.TAB). SMTP Log File: RCPT=ERELAY. In rare casese you could get this error when you are behind a Cisco PIX firewall that blocks ESMTP Auth Commands (check this page).
550 Account disabled
Negative Response if the Recipient account is disabled (ReceiveEnable = 0 in USER.TAB). SMTP Log File: RCPT=EDSBL
550 Mailbox unavailable
The Recipientís Domain part is Local but no User or Alias matches the Recipientís User part (USER.TAB or CMDALIASES Sub Directory). SMTP Log File: RCPT=EAVAIL
550 String does not match anything
Negative Response if VRFY is enabled (AllowSmtpVRFY = 1 in SERVER.TAB)
551 Server use forbidden
Mail command is locked because Xmail requires authentication from any sender (mail-auth in SERVER.TAB)
551 Server access forbidden by your IP
The Sender Domain is Listed in SMTP-RDNSCheck (SERVER.TAB). SMTP Log File: SNDRIP=ERDNS
The Sender Domain is Listed in CustMapsList Listed (SERVER.TAB). SMTP Log File: SNDRIP=EIPMAP
552 Too many recipients
Exceeded the maximum Recipients (RCPT TO:) available (Command Line: -Sr maxrcpts). SMTP Log File: RCPT=ENBR
552 Message exceeds fixed maximum message size
Exceeded the maximum message size (MaxMessageSize in USER.TAB or SERVER.TAB). SMTP Log File: SIZE=EBIG
557 Access denied
The User cannot post to the mailing list (check MLUSER.TAB RW attributes). SMTP Log File: RCPT=EACCESS

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