500 command unknown

[Anonymous]

Hi all

I have installed qpopper from the Eudora site on my Linux redhat 4.2
and can now do a pop3 and get my mail from the server.

When I send mail I get the error message 
500 command unknown 

When I look into the file /etc/services
I do not see the command listed.

Suggestions would be would be apriciated.

Jacob (Mettavihari)