Regarding email in Activity(Filtered) section

[vempatigopi]

Dear Community 
change the state field from waiting for requester to work in progress, once the requester replies to fulfiller emails/system generated emails.
Explanation: When fulfiller required more information from requester, then fulfiller changes the state to wait for requester and sends email to requester for more details, once the requester replied to that email, then state need to change to work in progress.

Hope you understood my requirement 
Kidnly help me to achieve this 

Thank you !

[Mark Manders]

You need to check on your own logic. The incoming email is handled through an inbound action or an inbound email flow. Within that action/flow you need to add the changing of the state.
You can find the flow/action you need, by checking an inbound email on a record that updated the record (an email in the activity). The related list of that inbound email will show you which inbound logic was used.