Espresso is a powerful permissions-based email client designed to completely eliminate spam as you define it from your Inbox.

Espresso's powerful email filter is based on a sophisticated challenge-response system. All messages from approved and trusted senders are immediately accepted. Espresso doesn't rely on deep header analysis, anti-spoofing techniques, heuristics, or Bayesian filters to eliminate spam. It simply looks for the messages you want to receive using sensible, yet powerful rules. With a selection of options available, you decide how to handle messages from unknown senders. Espresso delivers all the email you want to read and blocks all the email you don't want. It's that simple!

In addition to managing spam, Espresso's full-featured email client offers:

lightweight and portable application
powerful junk mail filtering based on permissions
filter messages using regular expressions
ability to add notes to individual messages
hide private messages from prying eyes
automatically blind copy on all outgoing mail
easily flag important messages
supports POP3, IMAP4, HTTP protocols
preconfigured for easy setup of Hotmail and GMail
built-in backup and restore mailbox
powerful spell-checker for outgoing messages
choose to save or delete messages when you send them
automatically mark messages as read when moved to trash