As per Facebook Messenger Platform Policy,

• Messenger opt-out: immediately respect all requests (either on Messenger or off) by people to block, discontinue, or otherwise opt-out of your using Messenger to communicate with them.

• Do not use Message Tags to send promotional content or other advertising, marketing, or solicitations including but not limited to the promotion of goods or services; to upsell; communicate new product announcements; request donations; send daily deals, coupons, discounts, or sale announcements; to send polls or user questionnaires. The use of tags outside of the approved use cases below may result in restrictions on the page’s ability to send messages.

• Pages may not facilitate person-to-person messaging, relays, or interactions that mask user identities from each other without giving individual users the ability to block other users within the messaging experience

• Sending spam as defined in Facebook Community Standards is not allowed. This includes behavior creating bots either manually or automatically, at very high frequencies; buying or selling feature privileges; facilitating or encouraging inauthentic behavior; failing to deliver promised experiences; directing users off of Facebook via deceptive or malicious URLs; and other substantially similar behavior designed to deceive or mislead users.

• Don’t use Messenger to facilitate direct conversations between people and healthcare providers or to send or collect any patient data obtained from healthcare providers

• Don’t share or ask people to share individual payment card, financial account numbers or other cardholder data within messages

Businesses should adhere to the above guidelines in order to be compliant with Facebook’s terms. Failing to do so may result in restrictions on the page’s ability to send messages or may also lead to legal action from Facebook.