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)