aggiungiamo queste regole a pf:

table <spamd> persist
table <spamd-white> persist file "/var/mail/whitelist.txt"
rdr pass on $ext_if inet proto tcp from <spamd> to \
         { $ext_if, $int_if:network } port smtp -> 127.0.0.1 port 8025
rdr pass on $ext_if inet proto tcp from !<spamd-white> to \
         { $ext_if, $int_if:network } port smtp -> 127.0.0.1 port 8025

e modifichiamo il file di configurazione di spamd secondo i nostri gusti (spamd.conf)