QuickBlox doesn't provide this feature out of the box cause of complexity for end users.
Let's imagine this situation:
- User registers in iOS app
- After this he should open his email and verify email address. It's a bit annoying, isn't?
You can verify user by QBUUser lastRequestAt field http://sdk.quickblox.com/ios/Classes/QBUUser.html#//api/name/lastRequestAt
After Sign Up - lastRequestAt field will be null. Only after real user login it will equal activity datetime