Apple's Mail is a good, general purpose e-mail client, but an active business life demands more from our correspondence. One of the more interesting e-mail options to come around in a while, the $40 Postbox from Postbox Inc. is a dynamic and even social e-mail client, able to display all recent correspondence with a contact, as well as post to Twitter and Facebook. Postbox's tabbed interface gives you more flexibility. A smart content areas collect all attachments in your inbox (without forcing you to dig around in messages), or all important information (say, photos or addresses) from a conversation. You can tag and create to-do items from messages, or even edit messages in your inbox to change the subject or add notes for future reference.
6 (and 7). MailTags and Mail Act-On
If you would prefer to stick with Mail instead of giving Postbox a try, adding this pair of plug-ins from Indev Software is like hiring two e-mail secretaries. The $30 MailTags ( Macworld rated 4 out of 5 mice ) adds a much-needed organizational boost with interfaces for tags and more powerful calendaring integration. It features type-ahead support for tags and everything you need to create events and to-do items that are associated with the original e-mail message. The $25 Mail Act-On ( Macworld rated 4.5 out of 5 mice ) adds more powerful rules and keyboard shortcuts for filing messages in their proper folders. You can colorize messages for followup or even apply rules when sending messages. In short, MailTags and Mail Act-On are an invaluable duo for getting more work done faster with Mail.