[server:~] # pkg_add -r popper
[server:~] # cat /etc/inetd.conf
...
pop3   stream  tcp     nowait  root    /usr/local/libexec/popper       popper
...
[server:~] # cat /etc/rc.conf 
...
inetd_enable=”YES”
...
[server:~] # /etc/rc.d/inetd start
===== Ubuntu =====
root@server:~# apt-get install qpopper
root@server:~# cat /etc/inetd.conf
...
pop-3           stream  tcp     nowait  root    /usr/sbin/tcpd  /usr/sbin/in.qpopper -f /etc/qpopper.conf
...