KShowmail is a POP3 mail checker for KDE. 

Main features: 
   o load mail headers from pop3 servers
   o display relevant header fields in a list view
   o display headers of selected mails
   o display complete mails
   o delete selected mails on servers
   o launch external programs like fetchmail or sendmail 
     via configurable menu entries
   o support multiple accounts
   o sound support
   o send complain mails to postmaster

WWW: http://kshowmail.sourceforge.net