I've used Eudora for several years.
It's easy to configure, you avoid the virus writers who attack outlook address books and it easily handles multiple accounts.
There's a free version that had an ad box in a lower corner of the display or you can upgrade to the paid version and get rid of the ad.
It's available in both winders and mac versions. I'm running it on my win2000 notebook and my wife has it on her imac.