Yesterday I experienced some issues with a school.
First that school has to emal domains, which is proving a bit tricky. So we updated our workflows to replace all teachers with the main domain that we need to use. I believe some teacher had the other domain, but apparently their email accounts got updated with the last sync and lots of them could not log in again as their email domains changed.
I though SDS had not capability to update users accounts or emails, but looks last night that was not the case. our school uses AAD to as well as local AD, local ID displayed no problems, but AAD reflected the updated.