How to disable single task default email in Visual Studio Workflow Manager ?

Hello Everyone,

I am using Visual Studio 2013 to create workflow in sharepoint hosted app.

I have used single task activity to assign task to user and used send email activity to send email to respective user.

In couple of environment it worked as i wanted.

But in specific environment, Two email are being sent to user.

1). From single task activity default email.

2). Send email activity.

So i want to disable default email of single task activity.

Or how can i disable default email of single task activity in that specific environment.

Any guidance or help appreciated.

Thanks,

Soyeb Malek