MailTags for Mac

From Indev:

With MailTags installed, you can add comments, due dates, projects and priority to your messages right inside your mail viewer window. You can then use this metadata as the basis for Spotlight searches, Smart Mailboxes, and Mail Rules. For example, you can create a Smart Mailbox that will show you all messages in project: "Great Novel" that have a due date in the next three days. MailTags also integrates with Mail Act-On to allow tagging of message via simple keystrokes, or by rules for receiving mail. For example, create an Act-On rule for the d key that will defer the due date of the message for 5 days.

Key Features

Integrated Interface

• Use MailTags' convenient side panel to add tags keywords, project, priority, notes to your messages.

• Create To Dos and Events in iCal directly from Mail and maintain the link between the original message and the items in iCal.

• Save your tags to your IMAP servers so you can access them from multiple computers.

• Display your tags in extra columns in the message list view. See due dates as they approach.

• Set tags automatically as you receive Mail by using MailTags actions when creating a Mail rule. Use with Mail Act-On to create keystroke rules to tag messages.

• Search for your tags by using Mail's search field, narrow the search to on keywords, projects or notes. Use simple and/or logic to find tags.

• Build smart mailboxes that search your messages for keywords, projects and even due dates.

• Construct Applescript work flows that access your MailTags data to use them in other applications.