..you may be out of luck, it was removed and you can't install it. Your options?

Windows Live mail. I like it, it was Hotmail but it does have more features now and once you download Windows live mail to your machine, you can check all your mail from right there. You may have to create a Live account but you can add other mail accounts, although I admit, I don't know which ones as I only use Live Mail.

http://explore.live.com/windows-live-essentials?os=other

or

Thunderbird, which is free and more like Outlook Express last I saw, which does allow you to add multiple accounts but may be a bit more tricky when setting up.

http://www.mozillamessaging.com/en-US/thunderbird/download/