Creation of task in the activity history is by defaul from Auto Reponse rule. You cannot stop from creating the record in Activity Histoty from an Auto-Response rule. This is by design.
You have options for not to show them in the Activity History 1. delete the record from Activity history object 2. Create a vf page and display the Activiy history records by filtering the Auto Response email record related to that case and add that vf page in the page layout and remove the standatd Activity History related list
Creation of task in the activity history is by defaul from Auto Reponse rule.
You cannot stop from creating the record in Activity Histoty from an Auto-Response rule. This is by design.
You have options for not to show them in the Activity History
1. delete the record from Activity history object
2. Create a vf page and display the Activiy history records by filtering the Auto Response email record related to that case and add that vf page in the page layout and remove the standatd Activity History related list
Please refer the below link
http://salesforce.stackexchange.com/questions/36464/why-does-auto-response-rules-create-an-email-on-that-particular-case
Regards,
Bhanu Mahesh