Mail & Notes Search Ability Lost

Hi folks.

Mail.app and Notes on El Capitan have both lost the ability to search. I've tested enough times. I know that mail and Notes are related.

• I can't make smart folders in Mail that actually work. They all come up with zero hits.
• In Notes, I can't use the search bar for terms, even of note titles.

I'm assuming this is spotlight. Can I delete the spotlight index and start it again for an overnight indexing? What's the path?

Cheers