Smart Mailbox is suddenly empty I created a Smart Mailbox this morning. I programmed it to hold all mail relating to my property purchase. This was successful. i checked it several times and it was full of all the relevant mail. 

This evening I went into the mailbox to find a back-dated mail, and it was empty. There is no mail at all. There is a message reading 'No Messages Selected'.

I am seriously freaking out! Help me!
You may have disabled Spotlight index searching which also affects Mail. 

To enable index search again, go to Settings > Spotlight > Privacy tab > Remove your hard disk from the list.