Microsoft, Microsoft 365, Outlook, SharePoint, OneDrive, Microsoft Teams, Microsoft Graph, Azure, and Entra are trademarks of the Microsoft group of companies. ImpressionsDirect360 is an independent provider and is not affiliated with, sponsored by, or endorsed by Microsoft.
Someone is expecting a message that never landed. Work out whether it was never sent, was filtered, or was rejected before you assume the mailbox is broken.
In Outlook, look in Junk Email, Deleted Items, and Archive. A filtered message is by far the most common cause, and it changes the whole diagnosis.
Open Settings, then Mail, then Rules. A rule made months ago that files a sender into a folder looks exactly like mail going missing.
If they got a non-delivery report, the full text names the reason and carries a message ID. Copy it in full — a screenshot of the first line is rarely enough.
Is it one sender to one recipient, or everyone in the company? One recipient points at filtering or a rule; everybody points at mail flow or DNS.
Open a ticket with the sender address, the recipient address, the approximate time, and the bounce text. With those we can trace the message through the tenant and tell you where it stopped.
Mail is missing for more than one person, the sender got a bounce, or nothing has arrived for over an hour — that is a mail-flow problem, not a filtering one, so tell us straight away.
If the fault turns out to be in the Microsoft service rather than your setup, we take it from there — you keep one point of contact.