Enable and Install the [Mailcontrol][1] module and then go to `admin/config/people/accounts` turn off the checkbox.

> This small module extends original Drupal 7 account settings page with
> the ability to globally turn ON/OFF all standard mails.

By default Drupal 7 provides no option to globally disable the following mails:

   - Welcome (new user created by administrator)
   - Welcome (awaiting approval)
   - Welcome (no approval required)
   - Password recovery

![enter image description here][2]


  [1]: https://drupal.org/project/mailcontrol
  [2]: https://i.sstatic.net/nzKLk.png