Qpopper is the most widely used POP3 server for UNIX, Linux etc., and can be downloaded from http://www.eudora.com/products/unsupported/qpopper/index.html
The latest version is v4.0.8
Download the source code archive from ftp://ftp.qualcomm.com/eudora/servers/unix/popper/qpopper4.0.9.tar.gz
wget ftp://ftp.qualcomm.com/eudora/servers/unix/popper/qpopper4.0.9.tar.gz gunzip qpopper4.0.9.tar,gz tar -xvf qpopper4.0.9.tar cd qpopper4.0.9
./configure --enable-specialauth --enable-standalone make mkdir /usr/local/man/man8 make install
You should be able to run it by typing /usr/local/sbin/popper and if all is well you should be able to telnet to the server from another machine by telnetting to port 110. You should see an +OK prompt.
Type quit to exit.
Qpopper is now installed and working.
If you want to run a server and you have a firewall running, you probably need to edit the firewall rules to allow access to port 110 (pop)
If using iptables use the following:-
vi /etc/sysconfig/iptables-config Add the following line near the bottom -A RH-Firewall-1-INPUT -p tcp -m tcp --dport 110 -j ACCEPT