How do I know which email address this is coming from?

If we do not ask for an email address to be provided or if someone types in an email belonging to another person (or if they fill out the form with someone else's name in it), how can we know from which email it is being sent?

The auto-responder sends out an email but where does it get the address from - how does it know where to send and where is this stored so we could know?

Unfortunately if you do not ask for an email address to be provided, or if they type an email address from another person, then it is not possible to know the email address of the user who submitted the form. 

Please note that the autoresponder only sends the email to the email address that was entered in the email field. If there is no email field, the autoresponder will not send. Likewise if they enter an email address of a different person, then the autoresponder will send the autoresponder email to that other person's email.

If you have multiple email fields on your form, then you can specify which email address the autoresponder will send to by opening the email settings and following the steps below:

1. Click the Recipients tab

2. Select the email field that you want to use from the Recipient Email dropdown

You can check out this guide for more info: Creating a Form Autoresponder
Cheers.