The qmail-moreipme patch by Scott Gifford prevents a problem caused by an MX or other mail routing directive instructing qmail to connect to itself without realizing it's connecting to itself, saving CPU time and in the most critical cases it takes away from a possible Denial of Service.
Expecially in the case that you are behind a firewall and qmail is not aware of the fact that your external IP must be considered as an IP of the server itself, just like as 0.0.0.0, 127.0.0.1 etc., don't forget to add it in the moreipme control file:
echo [your-firewall-ip] > /var/qmail/control/moreipme
