Thunderbird is the free email client from Mozilla (the home of Firefox).  Thunderbird makes it easy to organize, secure and customize your mail.

Cost: Free.
Availability: Online

Past Overall Rankings
2018: –   2017: –   2016: 187   2015: –    2014: –     2013: –
2012: –   2011: –   2010: –        2009: –   2008: 50   2007: 22

Comments from some of those who selected Thunderbird as one of their Top 10 Tools 

“Mozilla free e-mail program – light and easy to use, manages all my email accounts” Debora Gallo

“Mozilla’s open source email application helps me share ideas with friends and colleagues” Guy Boulet

“Email may be dead, but my email client continues to be a place of constant activity. Most of our corporate communications come by email, as do the various mailings lists I subscribe to, comments and enquiries from people around the world, and more. Email remains my primary communications tool precisely because it is asynchronous – I prefer to send and receive messages on my own schedule.” Stephen Downes

“A solid e-mail program that I’ve never had any problems with. Like Firefox, it has a ton of great add-ons.” Adam Kosh