I had been using Thunderbird for many years. It's very nice, and can be customized with the addition of plugins much like Firefox. But I really have to say that Thunderbird 3.0 is even better. I can't recommend it more highly!

I have only been using this app for about four months. I have only used Outlook but Thunderbird gives me the feel of Outlook. Love this app!!

I've been using Outlook for years at various jobs on Windows XP computers. Needless to say, I'm used to Outlook, and I like it a lot. I actually like Thunderbird as much as (if not more than) Outlook! The format is similar, though I feel Thunderbird is easier to set up and use than Outlook. Simple, straight-forward email.