Office 365 - disappearing incoming emails (sent to quarantine)
Users reporting that some incoming emails sent to their Office 365 mailboxes never reach them and don't even appear in Junk Mail folders.
A quick Office 365 message trace revealed that emails in question were sent to Office 365 Quarantine.
The quarantine can be accessed here and an admin can preview, download, or release the quarantined messages. As the screenshot below shows, the emails were sent to quarantine instead of the user's Junk Mail folder, because Office 365 Anti-Spam Policy identified them as High Confidence Phish (which was incorrect, the emails were completely legitimate text emails containing a single job sheet type PDF attachment).