Courier's Preference API allows you to list and update user preferences for the notifications they receive.
User Preferences API is coming to open beta
Provides the ability get all subscription topic preferences available for a specific user.
Get Preferences per subscription topic
Provides the ability to get user preferences for a specific user on a specific subscription topic.
Update Preferences per subscription topic
Provides the ability to opt a user in or out of receiving a notification and customize delivery channels.