Eudora was practically a CULT. I worked for one of their users who straight refused to use anything else, and one of my ongoing jobs as an admin was trying to get Exchange to play nice with it. It was maddening.
I fired it up several times for testing purposes, I don't get the hype, but man, for some people it was just the best damn software ever made.
It did its thing—internet email—really well. It was aimed squarely at the user with like a POP account, and it had a clean UI and plenty of features. For the time and use case, it was a fantastic client.
Outhouse tried to be too many things at once. Email client with HTML/rich text features that made it leave Microsoft crufties including mso: tags and the infamous J smiley all over your emails, contact manager, calendar. It was heavyweight, slow, and not quite there in terms of UI. But if you're an MBA type and you're committed to MSFT, or you're looking for a turnkey solution and it's this or Lotus Notes, Outhouse and Exchange sound like a win.
The Bat! was absolutely the best email client. ever. way ahead of eudora.
it was a massive step back when i switched to my first macbook in 2006 (the black one!) and started to use Thunderbird.
That said Thunderbird is fantastic now and great to see it get native Exchange support!
I fired it up several times for testing purposes, I don't get the hype, but man, for some people it was just the best damn software ever made.