Thunderbird

Thunderbird, a very user-friendly email client program, is also gaining market share. Even a simple look shows that Thunderbird is potentially better than Outlook Express, and while there seems to be little innovation with Outlook Express, Thunderbird continues to get better everyday.

Thunderbird has not achieved the market penetration that Firefox has, which is only reasonable because it has not had the publicity Firefox has yet. But usage of Thunderbird will grow as users of Firefox search for other great Mozilla products.