SYNOPSIS

       rblsmtpd opts prog

DESCRIPTION

       opts is a series of getopt-style options.  prog consists of one or more
       arguments.

       Normally  rblsmtpd  runs  prog.   prog is expected to carry out an SMTP
       conversation to receive incoming mail messages.

       However, rblsmtpd does not invoke prog if it is told to block mail from
       this  client. Instead it carries out its own limited SMTP conversation,
       temporarily rejecting all attempts to  send  a  message.  Meanwhile  it
       prints one line on descriptor 2 to log its activity.

       rblsmtpd  drops the limited SMTP conversation after 60 seconds, even if
       the client has not quit by then.

OPTIONS

       -t n   Change the timeout to n seconds.

       Blocked clients

       If the $RBLSMTPD environment variable is set and is nonempty,  rblsmtpd
       blocks mail. It uses $RBLSMTPD as an error message for the client. Nor-
       mally rblsmtpd runs under tcpserver(1); you can use tcprules(1) to  set
       $RBLSMTPD for selected clients.

       If $RBLSMTPD is set and is empty, rblsmtpd does not block mail.

       If $RBLSMTPD is not set, rblsmtpd looks up $TCPREMOTEIP in the RBL, and
       blocks mail if $TCPREMOTEIP is listed.  tcpserver sets up  $TCPREMOTEIP
       as the IP address of the remote host.

       -r base
              Use  base  as  an RBL source. An IP address a.b.c.d is listed by
              that source if d.c.b.a.base has a TXT record.  rblsmtpd uses the
              contents of the TXT record as an error message for the client.

       -a base
              Use  base  as an anti-RBL source. An IP address a.b.c.d is anti-
              listed by that source if d.c.b.a.base has an A record.  In  this
              case rblsmtpd does not block mail.

       You  may  supply  any number of -r and -a options.  rblsmtpd tries each
       source in turn until it finds one  that  lists  or  anti-lists  $TCPRE-
       MOTEIP.  It  also tries an RBL source of rbl.maps.vix.com if you do not
       supply any -r options. See http://maps.vix.com/rbl/ for  more  informa-
       tion about rbl.maps.vix.com.

       If you want to run your own RBL source or anti-RBL source for rblsmtpd,

       -B     (Default.)  Use  a 451 error code for IP addresses listed in the
              RBL.

       -b     Use a 553 error code for IP addresses listed in the RBL.

       -C     (Default.) Handle RBL lookups in a ``fail-open'' mode. If an RBL
              lookup fails temporarily, assume that the address is not listed;
              if an anti-RBL lookup fails temporarily, assume that the address
              is  anti-listed.  Unfortunately,  a  knowledgeable  attacker can
              force an RBL lookup or an anti-RBL lookup to  fail  temporarily,
              so that his mail is not blocked.

       -c     Handle  RBL  lookups in a ``fail-closed'' mode. If an RBL lookup
              fails temporarily, assume that the address is listed (but use  a
              451 error code even with -b). If an anti-RBL lookup fails tempo-
              rarily, assume that the address is not anti-listed  (but  use  a
              451  error  code  even  if a subsequent RBL lookup succeeds with
              -b). Unfortunately, this sometimes delays legitimate mail.

SEE ALSO

       tcpserver(1), tcprules(1), tcprulescheck(1),  fixcrio(1),  recordio(1),
       rblsmtpd(1),  tcpclient(1),  who@(1),  date@(1),  finger@(1), http@(1),
       tcpcat(1), mconnect(1), tcp-environ(5)

       http://cr.yp.to/ucspi-tcp.html



                                                                   rblsmtpd(1)