Help! With mail - it's gone

Uh-oh...

So there I was, on an iMac running SL and went to get mail, and the dock icon had a question mark on it. Apparently, I don't have mail (the native app). My wife has it on her login, but I don't. I have checked applications, etc. I hardly use it (using either my MacBook or IOS device), but need it none the less.

Can I download it... Or do I have to do a full reinstall (and how would one just install mail)?

Thanks in advance!