Broadcast Messages to facebook customer (Messanger)

I have created a bot using GitHub - RasaHQ/starter-pack-rasa-stack: 🎒Everything you need to build your first contextual chatbot with the open source Rasa Stack - includes files and training data. First the user will initilise the conversation. bot succefully send the reply

Rasa running - server A

CMS server - server B

I have the sender_id in CMS server B. Now the CMS server needs to send some notification to the user. so the CMS server B need to call the Rasa server A with the sender_id to send the message to user.

Please advise.