Mozilla Thunderbird is chock full of potential. Though it's as extensible as Mozilla's more famous browser, Firefox, Thunderbird lacks the same fanatical user support. A year from now, Thunderbird could be the emerging standard for e-mail software or just another fringe e-mail client.
Part of Thunderbird's eventual success will depend on the quality of third-party add-ons that enhance features and allow users more functionality and customization options. Though there's not nearly as many add-ons for Thunderbird as there are for Firefox, here's a quick guide to seven of my favorites so far.