My sent emails are all being bounced back as spam

Brenan Properties 0 Reputation points
2026-04-17T08:36:26.9766667+00:00

It's a newish email address I've set up as a point of contact for gathering certain information for a small group of people (tenants). Everytime I try to send an email to them i'm getting the following

Remote server returned '554 5.7.0 < #5.7.520 smtp;550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)>'

How does this unblock? I'm not sending spam, I'm sending a relatively similar email to the people to outlining 3-4 bits of information I need from them.

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  1. AI answer

    2026-04-17T08:36:41.9+00:00

    The error means Outlook.com’s spam filters are classifying the messages as spam based on content, sending pattern, or reputation, even if the messages are legitimate.

    To improve deliverability and get unblocked:

    1. Vary and simplify the message content
      • Avoid sending many nearly identical messages in a short time.
      • Change subject lines slightly and personalize the body (names, specific details) so they are not all the same template.
      • Remove or reduce:
        • Excessive links
        • Spam‑like phrases (urgent payment, prizes, etc.)
        • Large attachments
    2. Check that the account is not compromised
      • Review Sent Items, Deleted Items, and Inbox rules for anything suspicious (unexpected forwarding rules, auto‑delete rules, etc.), as these can cause reputation issues that trigger blocking.
      • If anything suspicious is found, follow guidance to respond to a compromised account and secure it (change password, remove malicious rules, etc.).
    3. Improve sender reputation and behavior
      • Send to people who expect the messages and are likely to read them.
      • Ask recipients to:
        • Add the address to their safe senders list.
        • Mark any misclassified messages as “Not junk” in their mailbox.
      • Avoid sending to invalid or non‑existent addresses repeatedly.
    4. Use Outlook.com sender support if needed
      • If messages still get blocked after adjusting content and behavior, use the Outlook.com sender support troubleshooting form (for Outlook.com system deliverability issues) to request help analyzing and improving the sender reputation.

    These steps help align with Microsoft’s anti‑spam protections so legitimate bulk or similar messages are less likely to be blocked.

    References:

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

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  2. Alice-N 13,405 Reputation points Microsoft External Staff Moderator
    2026-04-18T01:57:38.45+00:00

    Hi Brenan Properties

    I understand you’re having an issue where outgoing messages are being rejected with: 

    550 5.7.520 Message blocked because it contains content identified as spam. AS(4810). Are the recipients using Microsoft mailboxes (Outlook.com/Hotmail/Microsoft 365), and does the bounce come from ******@outlook.com? 

    Please follow these steps if the AI steps do not work: 

    1) Confirm the bounce is legitimate and capture the exact diagnostic details 

    Open the non‑delivery report (NDR) and scroll to “Diagnostic information for administrators” to confirm the precise reason and any additional details. Verify if the message is genuinely from ******@outlook.com / [email protected] / service.microsoft.com and not spoofed. 

    2) Try sender reputation steps  

    • If you run anti‑virus software, temporarily disable any feature named “Internet Email Auto Protect” or “Internet Email Protection”, then send a test email again.  
    • Add a clear display name to your outgoing email so the “send as” identity is easily recognizable.  
    • Send an email to yourself, open it, and reply to it. 
    • Add frequent recipients to your Contacts list. Using Contacts as part of reputation improvement.  
    • Ask recipients to add your address to their Safe senders list.  
    • Avoid sending to too many people at once (reduce volume/frequency if you suspect throttling/reputation impact).
    • See: https://support.microsoft.com/en-us/office/sender-support-in-outlook-com-05875e8d-1950-4d89-a5c3-adc355d0d652

    3) Check Outlook.com sending limits (especially for new accounts) 

    If this Outlook.com address is newly created, it may have a temporary low sending quota until credibility is established. See: Sending limits in Outlook.com - Microsoft Support 

    Please tell me how it goes. If the problem persists, please don’t hesitate to reply to this thread and I will be happy to help. Have a lovely day!   

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".    

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