@SabariS
Since the Flow needs to run on each users In Box, each user will need a copy of the Flow. The easiest way is to go to the Flow properties page and click on "Send a Copy" at the top of the screen:
Each user that you specify will receive a copy of the Flow along with instructions on how to import the Flow. Upon import, they will need to supply their own credentials - they Flow will run as that user.
Alternatively, each user could grant you access to their email - you would need a separate action to access each users In Box in your Flow - this obviously isn't practical.
