NAME

     filter-dnsbl — smtpd filter for DNSBL checks

SYNOPSIS

     filter-dnsbl [-h host]

DESCRIPTION

     filter-dnsbl is a filter for smtpd(8) which can be used to check new connections against a
     DNS-based Blackhole List (DNSBL).

     The options are as follows:

     -h host  Set the DNSBL host to be queried.

              The default host is dnsbl.sorbs.net.

     The remote IP address of new connections is used in a DNS query against the DNSBL.  If the
     remote address is listed, the connection is rejected, otherwise accepted.

SEE ALSO

     filter_api(3), smtpd.conf(5), smtpd(8)

HISTORY

     The first version of filter-dnsbl was written in 2013.

AUTHORS

     Eric Faurot <eric@openbsd.org>