Reporting on Approval Request Channels
Approval requests can be completed within Salesforce or outside of the system via email. This feature identifies which of the two is used for each approval request.
By adding the new Approval From Email field to a report, based on the Approval Request custom object, you can see whether someone advanced an approval request via email. This means they replied to an approval request email by entering one of the words "approve", "approved", "yes", "reject", "rejected", or "no" in the first line of their email response. Any other method of deciding on an approval request is considered to be approving it via Salesforce.
To create a custom report
After a number of approval requests has been decided on, you can run the report and see which requests were approved via email.
You must also ensure that the Enable Email Approval Response custom setting for Approvals System Properties is set to enabled. This is required for approvers to be able to approve approval requests directly in email, outside of Salesforce.