One of the features that is currently in beta in the Microsoft Graph API is an operation that will let you unsubscribe from any mailing list that supports the List-Unsubscribe header in a message that complies with RFC-2369 (https://docs.microsoft.com/en-us/graph/api/message-unsubscribe?view=graph-rest-beta). This can have a number of uses one that does come to mind is when you have staff that are leaving the company (or even taking an extended break where they won't be reading their email) and they have signed up to quite of number of mailing lists. As part of your deprovisioning process you can include a script that will unsubscribe from the emails in a Mailbox before you remove the account instead of deleting and hoping the NDR's do it for you. The RFC state the following for List-Unsubscribe 3.2. List-Unsubscribe The List-Unsubscribe field describes the command (preferably using mail) to directly unsubscribe the user (removing them from the list). Examples...
Pushing the Envelope in Messaging and Office 365 Development