Sendmail filtering for spams with access file

Issue

• It is possible to reject accessing from particuler hosts/IP(s)  to a sendmail server by those ways?

1.Adding lines into /etc/mail/access file as follows.

# vi /etc/mail/access

abc.example.com  RELAY
def.example.com  RELAY
*  REJECT

The above setting expects that only 'abc.example.com' and 'def.example.com' are allowed to access the sendmail server, and any other host is rejected.

2.Setting iptables' rules as follows.

# iptables -I INPUT -p tcp --dport 25 -j REJECT
# iptables -I INPUT -p -s 'IP ADDRESS1' --dport 25 -j ACCEPT
# iptables -I INPUT -p -s 'IP ADDRESS2' --dport 25 -j ACCEPT

This iptables setting is also similar meaming of the first one, which means that only the 'IP ADDRESS1' and 'IP ADDRESS2' can be accessed to the sendmail server, and any other host(IP ADDRESS) is rejected.