BookingNinja lets your customers choose if they want your marketing emails. This is disabled by default! To enable this, visit the Booking Fields section of the site and enable it. This will enable it across ALL active sessions automatically:

How Marketing Opt-In Works
When they tick that box, they're saying "Yes, I'd like to hear more from you!" directly; We’re not subscribing them to some mass ‘BookingNinja’ email list but rather getting permission for you - and only you - to contact them about marketing materials going forward.
You don’t need a marketing opt-in to send emails relating to the booking itself. Any email sent by BookingNinja itself is classed as a “service” email because it is always going to be about a particular booking. You do need it to send emails relating to your business outside of this booking, such as newsletters and promotional discounts.
What BookingNinja Is Legally Allowed To Do
You might be wondering: "Why can't I just have those boxes pre-ticked to catch more subscribers?" or “Can we have it so it’s tick to opt out instead”?
The UK privacy regulations (both PECR and GDPR) are pretty clear – people need to actively choose to receive your marketing. When boxes come pre-ticked, customers have to work to say "no" rather than actively saying "yes".
If we offered pre-ticked boxes, then we, and you, would unfortunatley be violating the law.
“Some organisations provide opt-in boxes that are automatically pre-ticked. However, the UK GDPR is clear that pre-ticked boxes do not give valid consent.”
Our philosophy:
We're all about keeping things transparent and putting your customers in control. Unticked boxes mean people make a deliberate choice to connect with you – which is not just legally sound but builds genuine relationships.
And honestly? There's another benefit here. When people actively choose to receive your emails, they're way less likely to mark them as spam down the road. Each spam report hurts your email reputation, making future emails more likely to land in the dreaded spam folder rather than the inbox where they belong.
In the long run, this opt-in approach actually helps keep your open rates healthy!