NAME

       smtpfront - SMTP Front Ends

SYNOPSIS

       smtpfront

DESCRIPTION

       The  code  for  SMTP is divided internally into two sections: front-end and back-end code.
       The front-end code handles the low-level details  of  the  protocol.   The  back-end  code
       handles the validation and delivery details in a protocol-independant fashion.

FEATURES

       The following features are common to all SMTP front-ends:

       o Validates senders and recipients according to ``mailrules'' processing.

       o If  $RELAYCLIENT is set, all recipient addresses not rejected by mail rules are allowed,
         and its contents are  appended  to  each  recipient  address.   Back-end  validation  is
         omitted.

       o Handles  RFC 2554 SMTP authentication.  After authentication all recipients not rejected
         by mail rules are allowed, and back-end validation is omitted.

       o Automatically handles either  bare  NL  or  RFC  821/2821  compliant  CR/NL  end-of-line
         conventions.

       o Rejects messages that exceed $DATABYTES bytes in the body.

       o Times  out connections after $TIMEOUT seconds of inactivity (defaults to 1200 seconds or
         20 minutes), or $SESSION_TIMEOUT seconds after the connection was established  (defaults
         to 86400 seconds or 24 hours).

       o Counts the number of "Received:" and "Delivered-To:" headers, and rejects the message if
         more than $MAXHOPS of either are seen (defaults to 100).

       o All error responses are logged.

       o Handles (ignores) RFC 1869 extended parameters on the ``RCPT TO:''  and  ``MAIL  FROM:''
         commands.

       o Initial greeting message is configureable by $SMTPGREETING.

       o Rejects bounce messages (messages with an empty envelope sender) that attempt to deliver
         to multiple recipients.

       o Optionally adds a fixup "Received:" header for hosts that have  different  incoming  and
         outgoing  hostnames or IPs.  Set $FIXUP_RECEIVED_HOST and $FIXUP_RECEIVED_IP if you want
         this header added.

BACK ENDS

       smtpfront-echo
              Uses the echo backend to simply echo back the sender and recipient parameters,  and
              the size of the data to the client.

       smtpfront-qmail
              Uses  the  ``qmail  validation  features''  to  validate addresses, and the ``qmail
              backend'' to deliver messages.

       smtpfront-reject
              If $SMTPREJECT is set, all SMTP commands are rejected with this  message.   If  the
              message  starts with a "-", a permanent error number is used and the leading "-" is
              stripped.  If $SMTPREJECT is not set, it execs its command line.

SEE ALSO

       pop3front(8)

        /usr/share/doc/mailfront/html/mailrules.html
        /usr/share/doc/mailfront/html/qmail-validate.html
        /usr/share/doc/mailfront/html/qmail-backend.html

        http://untroubled.org/mailfront/

                                                                                     smtpfront(8)