Master.cf file containing the following lines :

smtp inet n – n – – smtpd -o content_filter=autoresponder:dummy

smtp inet n – n – – smtpd -o content_filter=spamfilter:dummy

#
# Other external delivery methods.
#
# Autoresponder
#autoresponder unix – n n – - pipe flags=Fq user=autoresponse argv=/usr/local/sbin/autoresponse -s ${sender} -r${recipient} -S ${sasl_username} -C ${client_address}

# Spamassassin
spamfilter unix – n n – - pipe
flags=Rq user=spamfilter argv=/usr/local/bin/spamfilter -f ${sender} — ${recipient}