The following provides a summary of Microsoft Advisory issued on 16 May 2020 (Sat) which caused some users receiving duplicated emails these days.
Some staff & students (a small percentage of users as reported by Microsoft)
May 13, 2020, 5:35 AM
May 15, 2020 7:00 AM
Microsoft reported that a configuration change to the machine learning (ML) within the service unexpectedly caused emails to be marked as spam, and the reprocessing of those messages may have led to duplicate deliveries in some cases.
Some users reported that they received duplicated emails as unread at a later timestamp while those emails might had been read / replied to before.
Microsoft reported that they’ve completed monitoring the service and confirmed that the issue has been resolved. Next, they’re reviewing their configuration change procedures to find ways to prevent this problem from happening again.
A similar incident was reported on 7 May 2020 (Thur). Microsoft confirmed that it was caused by their service configuration issue which was fixed on 7 May 2020 (Thur) 3:15PM. Please refer to Microsoft Advisories here for details.