Add consent checkbox for emailing customers about their galleries or photos.
Enabling this option will add a yes / no option when a customer is creating an account, making a purchase. This is them giving you consent to send emails about the gallery like the early bird special, gallery expiring soon, etc...
Enabling this option will also add a yes / no option if you use the option to require an email address to view a gallery.
If the customer selects no, it will add their email address to the opt-out list in People -> Opt Out Emails so they won't receive any of those emails.