Block and Allow lists
O365 Spam Filtering does not allow you to block senders inside your organization (with an @mit.edu address). The interface will allow you to add a Kerberos email address to the allow or block list, but it will be ignored and stay on your list for a short period. If you try to add an MIT Moira list to your add/block lists, you'll get an error message. Same as with Kerberos accounts, you can't block MIT email addresses. The difference is the interface will let you know this with the error message. Although it may still remain on your list for a little while, it will still not have any affect on your email handling.
property=BlockedSendersAndDomains (System.String) Error= "email@example.com" is in your organization and can't be added to Blocked Senders..
Property Validation Failed.
It's as if the entirety of the MIT Community is automatically on an allow list that you can't override.