When a form is submitted you can apply some custom logic to the form submission data before any emails get sent out and the form data is saved. This is done with the form *Post Process Script*. For example, you could use some logic to set who the notification email should go to, change the email subject, integrate with a third-party API, and much more. You can set now custom headers for the email notification. (Note, this does not apply to autoresponders.) ``` {% do form.addEmailHeader('EMAIL_HEADER', 'email-header-value') %} ``` An example scenario could be if you needed to set some custom email headers to help your internal email system route emails from your website and filter for spam.