*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:log-smtp - [0:0]
-A INPUT -p udp -m udp --dport 161 ! -s 18.0.0.0/8 -j REJECT
-A OUTPUT -p tcp -m tcp --dport 25 --tcp-flags FIN,SYN,RST,ACK SYN -j log-smtp
-A log-smtp -o lo -j RETURN
-A log-smtp -m owner --uid-owner postfix -j RETURN
-A log-smtp -m owner --uid-owner nrpe -j RETURN
-A log-smtp -m owner --uid-owner 537644531 -j RETURN
-A log-smtp -j LOG --log-prefix "SMTP " --log-uid
COMMIT
