Identifying the compelling link

I'm wondering if there is any way for us to identify the SOURCE of the click that took our user to our form. For example if I have an email appeal that went out to our donors, and the donor found our email to be so compelling that they clicked on the form link and donated on our form, is there any way for us to know the origin of the compelling link?

I'm afraid that, as far as I know, we don't have that possibility with our forms. If I'm able to give you some better information I'll get back to you.

Thank you!