When you receives an email notifications and you click 'Reply', the reply message is typically sent to the email address listed in the From: header (email sender), which is firstname.lastname@example.org.
Mostly when you click 'Reply' you want to send a reply email to the submitter's email address, therefore you need to set a Reply-To address. A Reply-To address is the email address that the reply message is sent when you want the reply to go to an email address that is different than the From: address.
To set up Reply-To address :
Login to Formcubes' admin panel
Open your form workspace > Form Setting > Email notification setting
Enter one of your form's field name that contain email address you want reply to. If those field is