user did not send email

mara2021 811 Reputation points

Our users are in Exchange Online. One of our internal users (user A) received an email today (01/26/2024) from another internal user (user B) that was sent on 01/12/2024. User B stated that they did not send an email to user A on 01/12/2024. I did a message trace, and it did show that user A received the email today. I did a message trace on the sender user B, and I could not find an email sent from the user. What else can I do to find out what is happening. Thanks.

Microsoft Exchange Online
Microsoft Exchange Online Management
Microsoft Exchange Online Management
Microsoft Exchange Online: A Microsoft email and calendaring hosted service.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Shaofan Lv-MSFT 6,615 Reputation points Microsoft Vendor

    Hello @mara2021

    You could try Message Header Analyzer to check the email headers to see if there is a delay or the real sender to rule out spoofing.

    Kind Regards

    If the answer is helpful, please click "Accept Answer" and kindly upvote it.

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