Firefox and Thunderbird.
The learning curve is short beacuase of the similarities to IE and outlook.
Firefox may not be perfect but, it's the best out there.
Firefox is less likely to pick up viruses and such, the hackers seem to prey on IE.
I prefer Opera to Firefox. It was the option to rescale the page to my screen which got me using it but I've since used Firefox again and prefer Opera. For a mail client, I use Netscape/Mozilla. The advantage to all of these programs is that they are implemented across all of the popular operating systems unlike the MS offerings. That and the fact that they aren't riddled with system-deep vulnerabilities.
Opera is faster for me, although some things it doesnt work with and I end having to switch to mozilla firefox. I really dislike internet explorer. Boggles my mind why Microsoft cant come up with something amazingly better