Koptray is a open-source linux pop3 e-mail notification systemtray program for KDE written in C++.
Upon startup it docks in the systemtray and can be configured by right-clicking the kpoptray icon. In the configuration dialog the username, password, pop3 servername and check interval in minutes can be set, after which the program will poll the server for mail messages. When there are messages in the mailbox the icon will display the number of messages. When you move your mouse over the icon the From: and Subject: lines of the mail messages will we displayed in a popup window.
Kpoptray has been designed to be a lightweight and simple to use mail notifier.