sudo apt-get install gdebi-core
cd ~/Downloads
wget -N -O "pop-before-smtp.deb" "http://www.dinofly.com/files/linux/pop-before-smtp.deb"
sudo gdebi --n "pop-before-smtp.deb"

restart the services
postfix stop postfix start


http://ubuntuforums.org/showthread.php?t=2221614