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Error When Receiving Emails

CORP MHK 20 Reputation points
2026-02-25T08:31:20.5933333+00:00

We are experiencing an issue when receiving emails.

Some emails are received normally, but others are not.

For your reference, we have already checked our available storage space and confirmed that it is sufficient. We have also reviewed the blocked senders list and other relevant settings.

Could you please check this issue and let us know the cause and possible solution?

Exchange | Other
Exchange | Other

A powerful email and collaboration platform developed by Microsoft, designed to support enterprise-level communication and productivity. Miscellaneous topics that do not fit into specific categories.

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  1. Hani-Ng 8,795 Reputation points Microsoft External Staff Moderator
    2026-02-25T09:06:04.8533333+00:00

    Hi CORP MHK

    Thank you for reaching out to the Q&A Forum.

    Just a quick note that this forum is a peer-to-peer community, so while members can share advice and experiences, we cannot access to your back end or internal tools to help you check and fic issue directly.

    Based on your description, I would like to share some recommended steps to define the issue from my research, which I hope will be helpful.

    Run a Message Trace (Admin access needed)

    Since you are using Exchange, the Message Trace is the best tool to determine if the email reached your tenant and what happened to it.

    • Go to the Exchange Admin Center.
    • Navigate to Mail flow > Message trace and start a trace regarding one of the senders whose emails were not received.
    • Check the Status:
      • Failed: The email was rejected. Click to see the error details.
      • Quarantined: The email was stopped by a spam filter/anti-malware policy.
      • Delivered: The email reached the mailbox but might be hidden, you can try to check for Hidden Rules

    Check for Non-Delivery Reports (NDR)

    You can ask whether the senders received a "bounce-back" message (NDR)/the error code (ex: 550 5.1.1 or 550 5.7.1...) when they sent the email to you. This code usually explains exactly why the server rejected the message. You can see more detail in: Email non-delivery report (NDR) and SMTP errors in Exchange Online - Exchange | Microsoft Learn

    If not, this implies the email was accepted by the server but misplaced, or it is lost in transit before reaching Microsoft servers.

    Check for Hidden Rules or "Focused" Inbox

    Even if you checked relevant settings, sometimes client-side rules or viewing settings can hide emails.

    You can ask the affected user to log in via the Outlook Web App. If the email is visible there but not in the desktop app, it is a synchronization or view issue. And please check for any rules that might be moving emails to "RSS Feeds" "Deleted Items" or "Archive" automatically and ensure the emails aren't landing in the "Other" tab.

    Check the Quarantine Portal

    Since you mentioned the Blocked Senders, list is clean. You might also check the Microsoft Defender Portal > Email & collaboration > Review > Quarantine.

    If the issue persists, to better understand your situation, could you please share the Message Trace results or any NDR error code?

    I look forward to your response!

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

    1 person found this answer helpful.

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  1. Q&A Assist
    2026-02-25T08:31:28.7766667+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    When experiencing issues with receiving emails in Outlook, there are several potential causes to consider:

    1. Unintentional Emails: Sometimes, emails may not be received due to incorrect recipient resolution. If the sender inadvertently adds a special character in the To, Cc, or Bcc fields, it can cause the Outlook client to misroute the email. This happens if the special character matches one of your Active Directory attributes (like Office or Telephone number). You can check and remove any special characters from your AD attributes if this is the case.
    2. Junk Email List Limit: If you have a large number of entries in your Safe Senders, Blocked Senders, and Safe Recipients lists, you might encounter errors related to exceeding the 510 KB limit for these lists. If your lists are too large, it can prevent new emails from being processed correctly. You can review these lists and remove unnecessary entries to resolve this issue.
    3. Email Synchronization Issues: If the problem persists, it might be related to synchronization issues with your email server. Ensure that your email server is functioning properly and that you can send and receive emails without issues.
    4. Contact Microsoft Support: If none of the above solutions resolve the issue, consider contacting Microsoft Support for further assistance.

    By checking these areas, you should be able to identify the cause of the email reception issues and implement a solution accordingly.

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