How to rebuild the Spotlight index in iOS ?

Spotlight list deleted email entries on my iPad with iOS 5.1.1, including the first line of the deleted emails.

If I click on those entries, Mail opens some other email, not the one already deleted.

How can I force Spotlight to rebuild its index, finally ignoring deleted emails ?

I found ways to do that on Mac OS X, but not on iOS.

This is extremely annoying since this first line may be extremely confidential (the reason such an email was first deleted).

And no, it is not an IMAP account, but a POP one.

And yes, I can check off Mail in Spotlight Settings, but when I activate it again, the deleted emails entries reappear.