Entourage had always been my mainstay on the Mac, and out of all the clients, I still prefer its interface and features. Yeah, it barely knows what threading is, but it's still a sweet app with an achilles heel: It's database. I was losing email to this thing, people were getting messages they weren't supposed to, and Microsoft MVP's were telling me proper maintenance included rebuilding the database at least once a week, preferably twice. That's a joke.
Source: drunkenblog.com

Thunderbird was still buggy at the end of 2005.

Eudora 6.2.3 is like a blast from the past. It doesn't seem like much has changed on the outside for the past 5 years or more. The look and feel are show stoppers for me. Plus it has ads. Thunderbird is FREE and much much nicer. (10/17/2005) MacUpdate.com