Ah...

I didn't realize you were still on Outlook 2000. Yeah, probably best to phase that out, wonderful and robust as it has been.

This is just a thought, and I haven't explored too much of it, but you might want to take a look at what Google's offering. Besides gmail, it's now offering some pretty good (from what I hear) calendar functionality... I get the feeling that they're trying to move into that area of project management. If it's got the features you need and you're ok with the security... hard to go wrong with free. Again, don't know too much about it, but it was a thought.

If Weed is right, and you can buy Outlook 2007 on its own, that would still be my strongest recommendation. It's very, very similar to 2003, so the learning curve won't be too steep. It even has some additional functionality in message sorting (now they've got easy to use "categories" as well as flags).

So far as I know (which is a huge caveat), the only email software cheaper than Outlook don't offer nearly the same kind of features (calendars, tasks, etc.), and the only things beside it that offer the same features are serious project/customer management software that while incredibely useful will also be more expensive.

And I can attest that it runs just fine on XP. (Though my computer is also a fancy spankin' new dual-core, so I don't know how well it would run on a three or four year old machine.)

Oh... your final option would be to explore a web-hosted solution. I think there are even a few things like Hosted Outlook. Basically, you log into a web portal that holds your email as well as has all sorts of nifty other functionality things. A company called Blue Tie offers this for something like 5$ a month per user, and it has contact management (with groups, and shareable), calendar management (also shareable), tasks, the works. One nice big bonus it has online file storage for file sharing. You can put multi-gig files onto your account then sent an email with specific access codes to whoever you want to be able to access it. And Blue Tie's not the only one, I'm sure. The downside is that it's going to be slower to access than something that you have installed locally. And God help you if your internet goes down.