Can I send marketing messages to customers who ordered online?

It depends on the country, and WhatsApp needs opt-in too. Ask for consent when the customer orders, and give an easy way to stop messages.

• UK: a business may email or text customers who bought similar things from it, if it gives a chance to opt out.
• Saudi Arabia: marketing by email or post needs the person's prior consent and a clear way to stop.
• UAE: the consumer law protects consumer data and bars suppliers from using it for marketing.
• WhatsApp's business policy says businesses must get opt-in before messaging people on WhatsApp.
• Keep a record of who agreed and when.