Unable to get POP3 emails

[stavros]

Please I could need some help with a problem I face.
I have installed Red Hat 9, sendmail and created some mail users. When trying to get pop3 mails (POP3 is enabled) i get the error

ERR: Too few arguments for the USER command.

Even if I change my user
passwords every mail client shows that password is not authenticated. Please does anyone know anything about this?

The servers is listening to port 110. I have checked with netstat -na

[kkubasik]

do you know the pop3 protocol well enough to try it via telnet?
should go something like this

telnet 127.0.0.1 110
>helo localhost
>USER username
>PASS password
--or--
>PASSWORD password
>POLL
--or--
>LIST

something like that, you should get a more verbose error message, also what pop3 server are you using? check its config files to see where it logs error messages and look in them to see what the server is finding, or if its getting the connections at all (might be a firewall issue of some sort, allowing a udp connection, but no TCP, thus droping all packets, but looking like at netstat connection is game... [/speculation]