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Microsoft's mistake sends Outlook messages to Junk Email

Microsoft’s Exchange Server system had another snafu late last week, for a few hours all Inbox messages were sent to Junk Email instead!

The problem affected users of Microsoft 365 mail hosting.  It was caused by a ‘change’ that was applied to Exchange Server hosted by Microsoft.  As with other times, the update had unforeseen consequences.

For just under 2.5 hours on Wednesday, incoming email that should appear in the Inbox, instead was dumped into the Junk Email folder.

Microsoft fixed the bug fairly quickly but it took over a day for their systems to re-process emails and put them in the correct folder.  The message repositioning meant admins might have seen ‘delayed message state’ reports.

Check your Junk Email folder

By the time you read this, all messages should be in their correct folders. 

It’s worth checking the Junk Email folder to make sure there are no messages wrongly marked as spam.

Genuine messages tagged as Junk ‘false positives’ happen from time to time even in a properly working mail system.  Spam filters aren’t perfect and occasionally get it wrong by putting a message you want into Junk Email folder or worse, deleting the message completely!


Inbound mail was wrongly put into Junk Email on Wed, 26 May 2021 between 7:50 PM UTC and 10:15 PM UTC (from 12:50pm on US West Coast or 5:50am Thurs 27th on Aussie East Coast).

Repositioning messages (Junk Email to Inbox or other location) took until Thursday 27 May 2021 at 10:15 PM UTC or just over a day after the problem first occurred.

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