You can do that quite easily with your windows/linux client by just using telnet:

(bold text are commands from us, the rest are responses from the POP3 server)

telnet mx1.gosi.at 110

Trying 193.16.154.144...
Connected to seraph.gosi.at.
Escape character is '^]'.
+OK <22272.1140104162@mx1.gosi.at>

user username

+OK

pass password

+OK

list

+OK scan listing follows

1 2777
2 1861
3 2478
etc.

retr 1

+OK

mailheader/body/data
.

dele 1

+OK

quit
+OK
Connection closed by foreign host.