You can talk to the DSLR POP server just like your mail client can. Fire up your telnet client to host mail.dslr.net, and to port 110 (the default telnet port is 23). The conversation under Linux looks like this - what you type is in red

$ telnet mail.dslr.net 110
Trying 209.123.192.186...
Connected to mail.dslr.net.
Escape character is '^]'.
+OK <a211c376bfce5288278eacc7c597fcf5@gold>
USER steve@dslr.net
+OK Tell me your password.
PASS fatnessBozo
+OK Welcome aboard! You have no messages at all.
QUIT
+OK Done
Connection closed by foreign host.
$

If you don't get an "OK" after your password, you've done something wrong. The USER and PASS commands can be in lower case - they're just shown here in caps for clarity.