As we can see in the above screenshot when we open an email from Sales Hub it doesn’t search for Queue record in TO or FROM fields and the same way if we open an email from Customer Service Hub it won’t search  Lead record.

As we know in Legacy Web client there was no setting available to include or exclude them except Javascript so it took us some time to accept there might be some configuration or setting we might be missing. and with some research, my college provided the information providing below community query and it was helpful. thanks to Clofly Mao

https://community.dynamics.com/crm/f/microsoft-dynamics-crm-forum/361316/how-to-enable-the-email-from-field-to-include-queues-as-a-selection

So we can follow the below steps to add or remove entities from Model-Driven apps to show or hide them from Email entity but remember these are not only limited to Emails, if you remove any entity it will be removed from whole model-driven app.

1. Go to
   https://dvmske.crm8.dynamics.com/main.aspx?forceUCI=0&pagetype=apps
   and open app designer or best practice is to create a solution add your model-driven app to it and then edit the same.

   

2. Click on Entities which will open up a list of entities checked means added to the app

   

3.  Search for the entity missing

   

4. Check the entity and then scroll from Entity View to add forms or view to be available on the hub

   

5. Save and Publish

Same Way we can add lead fro the Customer Service hub and now Both entities will be visible in TO fields of the email.