With Radius CRM, you have the option to send an estimate by mail to the customer which is related to it. Also, the PDF estimate will be attached to the email. If you want to do not attach the PDF estimate, simply uncheck the checkbox Attach Estimate PDF
After sending the estimate to the customer, if you want to send again the estimate, there will be another email content because the initial estimate has already been sent. Now the customer may want the estimate again and in all cases, this content will be different. Go to Setup-> Email Templates -> Estimate Already Send to Client to edit the email content when sending the estimate to your customer for a second time.