Disallow Users from Sending Attachments in Messages (Custom Permission)
In the new January '22 release, we introduced a Custom Permission that controls which users are allowed to send attachments in their SMS messages.
Prevent Users from Sending Attachments in Messages (Custom Permission)
- Go to Setup.
 - Create a new Permission Set.
 - Assign one or more users to the Permission Set.
 - Apps > Custom Permissions.
 - Click Edit.
 - Add the Custom Permission: "simplesms.Prevent Textey Attachments".
 - Click Save.
 
Now Login to the assigned user and check the Blackthorn Messsaging Messenger!