To successfully use Case Feed in conjunction with Email to Case Premium please ensure the following:
- Select Case Feed Layout on the Setup Page.
- Ensure you are Using a "Feed-Based" Case Page Layout.
- Enable Case Feed Actions and Feed Items through Case Support Settings.
- To access your Case Support Settings, navigate to Setup | Build | Customize | Cases | Support Settings.
- Add the "Answer Customer" Action to your page layout.
- To access your page layouts, navigate to Setup | Build | Customize | Cases | Page Layouts.
- Ensure email deliverability is set to "All Email" in your Org via Setup | Administer | Email Administration | Deliverability.
- Ensure that all Case Feed enabled Page Layouts have been converted off of the "Page Layouts for Case Feed Users" section into the main "Case Page Layouts" section per the following Salesforce help and training article: Convert Page Layouts for Case Feed Users to Case Page Layouts.
For more information on Case Feed, review this Salesforce help and training article: Case Feed Overview.
Please upvote the following Success Community idea for a DML Option to disable automated Feed Item creation.