I have no mail,

 my program folder opens with this message,“This folder contains no data and no operations can be performed”

Same thing happened to me tonight. I just recently upgraded to version 7, after the same thing happened in version 6. In addition to the error message, the mail tab is missing; I just have Calendar, Tasks and Contacts tabs. 

Hello,
sounds like you accidentally hid the Mail item in the left-side menu.
Just right-click any other item in the menu and check Mail to show again.

Regards,
Olivia

Thanks Olivia, that worked for me!!