I never lost a single piece of e-mail using Eudora from 1996-2001.

I second this, and actually have been a Eudora user since 1994 when it was a standard part of my University's Internet access package. I can't say that those early versions were particularly stable, but in terms of losing email, that never happened to me. I only recently switched to TheBat! because of its better filtering and other bells and whistles.