Hi dw76,
Do you still have the copies of the emails whose sender was identified as the “PrinterX”? If yes, please provide the mail header of one old email and a problematic email with us so that we can compare the difference and do investigation. To check the email’s mail header, you can double click it in Outlook Web App, and then click More actions> view message details. Or you can click double click it in Outlook client and click File> Properties> Internet heads.
And since the mail headers usually contain private information, please paste it in the reply of my Private Message. To read the PM, please refer to the steps below:
1. Go to "Your details" section on the right side of the community site
2. Click Private messages.
3. Click the subject title of the response to read the message.
Thanks,
Henry Huang