Outlook.com Hotmail emails blocked with error 554 5.7.520 AS(4810)

Khawaja Javed Iqbal 0 Reputation points
2026-10-15T08:41:59.49+00:00

My personal Outlook.com (Hotmail) account has been rejecting outgoing business emails for three days with error 554 5.7.520 AS(4810).

I send only 8–10 emails daily. I do not attach catalogues or other files, and my recent account activity appears normal.

A plain-text test email to an external Gmail address was sent without an immediate rejection, but my regular business emails have been rejected with this error.

How can I request a review of this outgoing spam-filter block and restore normal email delivery?

Thank you.

Outlook | Web | Outlook.com | Email
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  1. SD - IA 181.4K Reputation points Independent Advisor
    2026-10-15T10:25:07.3933333+00:00

    Hi,

    but my regular business emails have been rejected with this error.

    Did it include a signature?

    If so, please remove it and then verify.

    https://yourwindowsguide.com/2026/04/how-to-change-signature-in-outlook.html

    Second: I take it that the Business email wasn't in plain text format, is that correct?

    Refer to:

    550 5.7.520 Message Blocked Error in Outlook (4810): How to Fix It

    https://yourwindowsguide.com/2026/09/550-5-7-520-message-blocked-error.html

    I look forward to hearing from you to get the results of the troubleshooting.

    A Windows MVP writes content on the above website, so it is safe. However, do watch out for the ads. It should translate into your Browser language automatically.

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  2. AI answer

    2026-10-15T08:42:23.4+00:00

    For a personal Outlook.com/Hotmail account, the most relevant next steps are:

    1. Send a simple test message from Outlook.com with plain text only.
      • Since a plain-text message to Gmail was accepted, the block is likely being triggered by the content of the business emails rather than a general account-wide send failure.
      • Remove anything that can look risky to spam filters, such as links, repeated text, or large/embedded content, and test again.
    2. Review the message content that is being rejected.
      • The 5.7.520 error is used when a message is identified as spam by mail filtering.
      • If a simple message sends successfully, add content back gradually to identify what triggers the rejection.
    3. Check the account for compromise-related changes.
      • Review the Sent folder for unfamiliar messages.
      • Review mail rules and forwarding settings for anything unusual.
      • If anything suspicious is found, change the password and enable MFA.
    4. If the issue is specifically with delivery to Outlook.com/Hotmail recipients, use the Outlook.com sender support troubleshooting/contact form.
    5. If the rejection is from the recipient side, contact the recipient’s mail provider.
      • When errors indicate the message was blocked as spam by the recipient server, the recipient provider may need to unblock or whitelist the address.
    6. If Microsoft support review is needed for Outlook.com account sending restrictions, use the Outlook.com support entry points.
      • In Outlook.com, use Help on the menu bar, enter the issue, and if self-help does not resolve it, go to Still need help? and select Yes.
      • If sign-in or self-help does not work, use the Outlook.com support contact option provided in the support article.

    Based on the symptoms described, the strongest evidence points to a content-triggered spam classification rather than a total sending ban, because the plain-text Gmail test was accepted.

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

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