rblsmtpd
Whitelisting and Blacklisting IPs
You can whitelist a specific or range of IPs by using the RBLSMTPD environment variable. The most common way of doing this is by creating a rule for inclusion in the tcprules file, most commonly tcp.smtp. Add a line containing the IP address, an allow, and RBLSMTPD as the environment variable. For example :
192.168.1.1:allow,RBLSMTPD=""
When a connection attempt is made by 192.168.1.1, rblsmtpd will skip the RBL check and immediately allow the connection. Conversely, you can also blacklist an IP using a similar technique, but by specifying an error response as the RBLSMTPD variable. For example :
192.168.1.2,allow,RBLSMTPD="-rblsmtpd deny: take your spam elsewhere!"
This will cause any connections from 192.168.1.2 to be immediately dropped with a message of "rblsmtpd deny: take your spam elsewhere!"