PopTray is a mail notifier with a large round of features. It can offer you the following:

• Unlimited number of Accounts
• Show number of messages directly on the TrayIcon (rotating by account)
• Quickly preview a message
• Delete messages from the server without downloading them
• Identify a message according to your criteria
• Configurable hot-keys/mouse-buttons/command-line options for most functions
• Plug-in support for protocol and notification
• Spam management using rules and white/black lists
• Multiple notifications (play sound, pop-up, etc)