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550 5.7.520 Message blocked because it contains content identified as spam.

ic 0 Reputation points
2025-10-15T13:27:21.33+00:00

222

Microsoft Outlook (Web Version) keeps informing me that my emails are "undelivered".

the message i received is attached as a screenshot for reference.

In short, it contains this: "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)>'"

Would anyone be able to advise how I could remove my email address as spam? It is a personal email address and I do not send more than five emails a day on average.

Outlook | Web | Outlook.com | Email
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  1. Thomas Andrei 0 Reputation points
    2025-10-16T08:10:27.51+00:00

    I have the same issue.
    I tried sending my email again without Rich Text. And it works, thanks.

    However, I can't just stop sending Rich Text forever.
    So what can I do to be able to send Rich Text emails again?

  2. EmilyS_726 15,880 Reputation points Volunteer Moderator
    2025-10-16T01:21:37.9033333+00:00

    These emails include attachments and were sent in Rich Text format, correct? This issue is not on your end but on Microsoft’s. It occasionally occurs when Microsoft’s anti-scam system becomes more aggressive. For instance, during periods of increased phishing activity, emails that use Rich Text formatting and include attachments are more likely to be blocked automatically. When that happens, there are a few workarounds you can use until Microsoft’s filters ease up again:

    1. Convert the email format to plain text. This is usually the quickest and easiest fix. Instructions can be found here: Instruction can be found here: https://support.microsoft.com/office/change-the-message-format-to-html-rich-text-format-or-plain-text-in-outlook-338a389d-11da-47fe-b693-cf41f792fefa
    2. Share the file via a OneDrive link so the recipient can download it directly.
    3. Compress the attachment into a .zip file before sending it.

    These steps should help you get around the temporary filter restrictions.

  3. John Oliver 11,620 Reputation points Independent Advisor
    2025-10-15T14:41:55.76+00:00

    Hello ic, Thanks for posting this in our community. I understand how frustrating it must be to have your personal emails blocked and flagged as spam, especially when you're only sending a few messages a day.

    When you send an email, are you attaching any files? If yes, this might be contributing to the issue.

    Some users have reported that emails containing attachments from their Outlook.com mailbox are being blocked with the error code 550 5.7.520 Message blocked. While we work on a fix, there’s a workaround you can try.

    Instead of attaching the file directly, you can send it as a OneDrive link. To do this, reply, forward, or create a new email or calendar event. Then select "Attach." If the file is already in your OneDrive, choose "OneDrive." If it’s not, choose "Upload and share." Pick the file you want to send and select "Share link." You can also use the "Copy link" option from OneDrive or Office and paste it into your email.

    This method helps avoid triggering spam filters that may block emails with direct attachments.

    These articles might help you resolve the issue:

    1. Fixes or workarounds for recent issues on Outlook.com
    2. I receive a 550, 553, or relay-prohibited error when sending email messages

    Kind regards,

    John Oli

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