Q: delete, already deleted emails from spotlight search

after deleting them (and make sure they are also deleted from "deleted" box on mailmoxes)

try to reset all settings.

should do the trick.

You would need to restore your phone as a new device (not from backup) to clear the cache and prevent the detection in spotlight searches.

Contacts should be on your computer or cloud service, photos taken by the iPhone should be imported to your computer.  iTunes media should be synched with your computer and reside on your iTunes library. 

So, there is no way around this? This is such a pain in the button. My client doesn't use cloud. I am surprised this bug has been around since 2009 and still not fixed. What's up with that?

I found out a way to do it with gmail....no idea if it works with other email providers.

Login to gmail from a computer and clear out your trash.

Go to settings/Labels and make sure the checkbox that says "Show in IMAP" in unchecked next to "All Mail"

Save settings

Go to your device (worked for iphone 5 and ipad mini for me) and delete your email account and then put it back on your phone.  These emails should now be removed. What a pain.  Good luck!