There are some previous posts relate to POP3. Actually, I have the same problem, and I couldn't find the answer.
My system is Redhat 6.0, and I followed the instruction to enable POP3. But I still couldn't telnet to 110 port. It said "trying Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Connection closed by foreign host
Anything else I need to check up?
Here is the /etc/inetd.conf and /etc/services files
pop-3 stream tcp nowait root /usr/sbin/tcpd ipop3d
pop-3 110/tcp # POP version 3
pop 110/tcp # PostOffice V.3