# Add these lines to your ~/etc/sendmail.cf to implement the POP-before-SMTP
# anti-spam configuration.  Substitute a tab character(s) for [tab] below.

Krelayers hash /etc/relayers
Kdequote dequote

#############################################################################
# Anti-Spam Support:  Limit SMTP relaying to previously authenticated users #
#############################################################################
Scheck_rcpt
R< $+ @ $=w >[tab]      $@ OK
R$+[tab]                $: $(dequote "" $&{client_addr} $) $| $1
R0 $| $*[tab]           $@ OK
R$* $| $*[tab]          $: $(relayers $1 $: ERROR $)
RERROR[tab]             $#error $@ 5.7.1 $: "550 SMTP relay denied, authenticate via POP/IMAP first"
R$*[tab]                $@ OK