When it comes to email notifications on Case and Lead objects, Auto-response rules and workflow email alerts provide similar functionality. However, they differ with respect to the limitations they have.
The following table lists some of the differences between workflow alerts and auto-response rules to help you determine which process to use:
|Type of Process||Designed For||Runs When||Sends Email To||Number of Emails Sent|
|Workflow email alerts||Notifications to interested parties.||A case or lead is created or edited.||Anyone you choose.||Sends one email per email alert. Each workflow rule can have up to:
|Auto-response rules||Initial response to the contact who created a case or the person who submitted the lead on the Web.||A case or lead is created.||Contact on a case or the person who submitted the lead on the Web.||Sends one email based on the first rule entry criteria it matches in a sequence of rule entries.|
The emails sent thru’ Auto Response Rules are tracked in Email message object against the Case record while workflow email alerts cannot track the emails sent. The emails tracked in Email message object includes all the email exchanges between the support agent and the customer.
References : https://help.salesforce.com/articleView?id=rules_differences_auto_workflow.htm&type=0