- Each user that responds to cases using the New Comment page will require a license.
- You can purchase 50 licenses, for example, and identify 50 specific Salesforce users that get them.
- Sales & Marketing Users, for example, do not generally need licenses.
- External users sending emails into Salesforce do not require a license.
- Each internal user that responds to cases using the Email Distribution feature will require a license.
- Each internal user that needs to see or interact with the Timeline will require a license.
- A single license is required for the "context user" that you specify during the initial setup.
- The context user is ideally a dedicated API user and can be changed by navigating to Setup > Develop > Email Services > Email to Case Premium and editing the routing address(es) listed.
- If you do not have a dedicated API user, it is generally best to use (and license) the user you specified as the Automated Case User under Setup > Customize > Cases > Support Settings.
- Self-Service, Customer Portal, and Partner Portal users do not need licenses because they don't interact with Email to Case Premium directly.
- A license is required to configure Email to Case Premium.
For more information, see "Assigning Licenses for Installed Packages" by clicking on Help & Training at the top of your Salesforce.com