master.cf

smtp      inet  n       -       n       -       -       smtpd
        -o content_filter=lmtp:unix:/tmp/dspam.sock


localhost:10026 inet  n -       -       -       -        smtpd
  -o content_filter=
  -o receive_override_options=no_unknown_recipient_checks,no_header_body_checks
  -o smtpd_helo_restrictions=
  -o smtpd_client_restrictions=
  -o smtpd_sender_restrictions=
  -o mynetworks=127.0.0.0/8
  -o smtpd_authorized_xforward_hosts=127.0.0.0/8


dspam.conf

DeliveryHost        127.0.0.1
DeliveryPort        10026
DeliveryIdent       localhost
DeliveryProto       SMTP