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Nothing is visible, its a really really old version.
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the whole program looks different.
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Nothing is the same, it looks like Ive never had anything on my mail program.
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Even my junk mail, nothing is there at all, my preferences are all missing too. Outgoing mail and incoming are all blank!!!!
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the whole program [display?] is just plain blank
It sure sounds like you're not using the same version of Mail that you had been using.
Are you sure you haven't recently been doing some "spring cleaning?" Maybe deleted the newer version of Mail and now have only an earlier one?
What is the version number (just select its icon, in Finder and press command-I)? Or select the Mail->About Mail menu.
Are you saying there is absolutely no "Mail" app in TM? No janescomputer(whatever your computer's Home folder is)/Library/Mail folder?
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But who bothers to back up emails?
I do. And I hope you now will as well. 
My email is FULL of vital info - I've even referred to emails I received years ago at times.
There is no limit to the number of accounts you have in Mail as far as I know. I've had 6 or 8 at times, since I sometimes have test accounts for clients etc. No problems. And if they're all on one Mac, which I HOPE you're backing up regularly using Time Machine or SuperDuper, then you probably will never face the situation of having lost all your emails again.