Mail Beacon (OS X) for Mac

Mail Beacon is both a mail checker and online e-mail client. Mail Beacon checks an unlimited number of POP3 and IMAP accounts, and instantly notifies you of new messages. You can then read, reply, and filter e-mail on the server without downloading a single message. You open Mail Beacon, clean out any spam, and quickly respond to important messages, all before opening your regular bulky e-mail client and downloading your messages to disk. It checks an unlimited number of e-mail accounts, supports both POP3 and IMAP4, and has a built-in address book, reminders, password protection, and two unique views: Browse and List. It filters e-mail on the server; sorts by date, subject, or sender; and has an easy-to-use interface.

Version 2.1 features unspecified improvements and bug fixes.