Starting in the Winter 15 release, Salesforce delivered a Reply-To-All option within Case Auto-Response rules. This helps ensure that all addresses copied on the original case creating email are notified that a case was created, and also aids in making sure their replies are added to the existing case rather than opening a new one. Due to Platform limitations, the standard Reply-To-All feature is not applicable for cases processed via Email to Case Premium. Long before this feature was available, Internet Creations has developed a workaround to this particular gap with the help of Case Teams and Workflow. Please review and follow the steps below to implement this workaround. Just to note, your organization must have Enterprise or Unlimited Edition in order to utilize Case Teams and Workflow.
Step 1 - Add a Role for the Case Team Members. Navigate to Setup > Customize > Cases > Case Teams > Case Team Roles > New. We recommend the role "CCed on Email" to help distinguish that the new Case Team Member was originally CCed on the inbound email.
Step 2 - Case Teams must be enabled within Email to Case Premium's Inbound Configuration Settings. Navigate to the Email to Case Premium App > Settings Tab > Jump To Inbound Configuration (on right) > Check Auto Add Case Team Members. From the Team Member Role for Auto Add picklist, select the Case Team Member Role created in Step 1. At this point, any existing Contacts or Users CCed on an email can be added to a Case Team and receive an auto-response, but if you would like to include foreign email addresses, you must also enable Auto Add New Contacts.
Step 3 - Create a new Workflow Rule that fires only on case creation. The criteria should include (and can exclusively be) Subject does not contain [Email Loop Protection] to support email loop protection.
Step 4 - Create a new Email Alert. Select your template, preferably one of the Email to Case Premium Auto-Response templates as they contain the proper Thread Id already. From the Search picklist, choose Email Field and select either the Contact Email or Web Email field. Also from the picklist, select Case Team and add the Case Team Role created in Step 1. At the bottom, select the appropriate From address for the email. Save.
Step 5 - Click Done then Activate your new rule.
Note: Make sure to uncheck "Use Active Auto-response Rule" on the Email to Case Premium Inbound Configuration screen AND to move all of your Auto-Response rules over to Workflow.