do you mean the email function already there in the Mozilla program? It's fine, I just prefer a standalone. You shouldn't need the separate Thunderbird program, I'd think...but they say this about it..

"Our intended customer is someone who uses Mozilla Firebird (or another stand alone browser) as their primary browser and wants a mail client based on mozilla that "plays nice" with the browser. In addition, by focusing solely on stand alone mail, we believe we can make some dents in the overall footprint and performance of the mail client by removing components and chrome we don't need. On top of that, the UI becomes much cleaner as a stand alone application as opposed to being part of the mozilla suite."

I presume it is a pretty good program by itself..(as you might guess, *I* don't exactly need another one..*grin*)