
Ok, I just disabled the Send connector on Exchange, sent a scan to the second mailbox and it was sitting in the queue. I can't use Message Trace because it only lets me select on-premise mailboxes. I've looked in the Exchange Toolbox Queue Viewer and it's empty.

The scanners send to our on-premise Exchange server which just relays to O365. You said in your original post that the scanner logs are showing the email sending fine but where does the email go after that? If it goes through a internal forwarder and then an external one you should check each step along the path to see where the email disappears. So the trace didn't show it, yet the scan was delivered when I sent it to both at the same time.ĭid you run the trace with the Message-ID from the email headers? But when I then sent two individual scans - only the one to the second mailbox is there. I just looked and the scan sent to both at the same time shows both recipients. Again the second one got it - and it shows up in a message trace.Įdit: We have a rule that copies all inbound and outbound email to a 'journaling' mailbox. Then I sent individual scans to both mailboxes. And I searched on both at once and each individually. Check a message trace - it showed nothing for either mailbox.

Sent a scan to both emails, it showed up in the second mailbox within 30 seconds. Can you try sending the scan to the working mailbox and the non working one in the same email and then look the message up in Exchange admin center > mail flow > message trace? If that message doesn't show up for both mailboxes, I would look at the sending side and make sure nothing is being filtered there.
