I'm using Opportunity module and I want to display popup notifications to the followers of each Opportunity thread when a new message is sent.

I can see a popup notification if I click on a user and send a message directly to him but If I click "Send Message" on the Opportunity thread I only get a "1" in the top right chat and no popup notification. 

How can I convert this notification into a popup one like when sending a message directly to a user?