I wrote this after seeing many customers struggle with Outlook when they don't have to. Many people don't have an Exchange mail server and therefore don't need to put up with Outlook.
On Windows, Gmail does most of what Outlook can do, but faster, and is more satisfying to use because you don't have to put up with random crashes. Check out Brant Tedeschi's excellent guide to switching from Outlook to Gmail.
What if I want to send "From:" my company address using Gmail?
You can. See these step-by-step instructions from Google.
But I want to use Outlook without Exchange!
Outlook was designed and built mainly for one purpose - to talk to an Exchange server. Everything else it does is implemented half-heartedly. That means you're going to see slower performance, more bugs/crashes, and more potential for loss of mail than if you were just using it to talk to an Exchange server.
How can I tell if my company uses Exchange?
Ask your IT guy.
But I have Exchange, am using Outlook, and it's still slow.