Unintentional email delivery

BK 0 Reputation points
2026-02-24T08:54:24.9733333+00:00

Hi, we have an issue where user A send an email to someone outside the organization, but user B receives the email. Also, when someone outside the org send an email to user A, user B receives it as well. Please note this issue is not user A or user B specific, as it happens randomly to all users. *EDIT No forwarding or shared mailboxes are setup between users

Microsoft 365 and Office | Other
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  1. AI answer

    2026-02-24T08:55:07.0533333+00:00

    The issue you are experiencing, where emails sent by one user are being received by another user, could be related to several factors in Microsoft 365. Here are some potential causes and troubleshooting steps:

    1. Email Forwarding or Rules: Check if there are any forwarding rules set up in the email accounts of user A or user B. Sometimes, users may inadvertently set up rules that forward their emails to another account.
    2. Shared Mailboxes: If user A and user B have access to a shared mailbox, emails sent to the shared mailbox may be appearing in both users' inboxes.
    3. Mail Flow Issues: There may be a misconfiguration in the mail flow settings within your Microsoft 365 environment. It is advisable to review the mail flow settings and ensure that there are no unintended configurations that could cause emails to be misrouted.
    4. Email Client Issues: If the users are using different email clients, there may be a client-specific issue causing this behavior. Testing with Outlook on the web can help determine if the problem persists across different platforms.
    5. Contact Microsoft Support: If the issue continues, it may be beneficial to contact Microsoft Support for assistance, as they can provide more detailed insights into your specific setup and any underlying issues.

    By investigating these areas, you may be able to identify the root cause of the email delivery issue and resolve it accordingly.

    AI-generated content may be incorrect. Read our transparency notes for more information.

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