Message identified as SPAM "Remote server returned '550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)'"

Carl Pullen 500 Reputation points

Remote server returned '550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)' Today i have received an email returned as spam. This was from an addressee who I correspond mostly, being a family member and I was sending them an important document. Both of these are Microsoft accounts (Hotmail and Outlook), both accounts are listed under my family 365 account, both using Microsoft Outlook and no other system for sending and receiving emails. Can you tell me why this is the case and how I am able to stop this in the future?

A family of Microsoft email and calendar products.
3,089 questions
Outlook Management
Outlook Management
Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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52 answers

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  1. Víctor Marcos Garcés 145 Reputation points

    I'm having the same issue on 6th of November 2023. Trying to e-mail contacts I have previously sent e-mails thousands of times before. Really frustrating, indeed.

    29 people found this answer helpful.

  2. Stephen Z 95 Reputation points

    Update 22:30 6/11/2023 AEDT (GMT+11)

    I have read through all comments. It seems like this problem only happens on the web client ( in browser and "New Outlook App", which is essentially an PWA).

    I have personally tried using the Outlook app on my Android phone. It works without any issue.

    And as ALAN stated on 22:19 6/11/2023 AEDT (GMT+11):

    If this helps anyone. You can send emails with attachments. But only through the Mail desktop app "switched to old outlook" it will not send if switched to new app. Hopefully Microsoft will have this issue sorted soon!

    The old Outlook app (a real app) on PC is unaffected as well.

    Temporary Solution

    So, so far if anyone is affected by this issue, try using the mobile app or the classic UWP outlook app instead. And please share your experience below if possible. (I have not yet tested the Outlook app bundled with Office, which in theory should also work)

    Hopefully it helps with anyone who is experiencing the issue.

    Original Answer

    Same things happening today. I'm in Australia. I've conducted some tests. As long as the email contains any attachment, it cannot be sent through.

    From To Result
    Outlook to Outlook Rejected by "recipient's email provider"
    Outlook to Gmail Rejected by "recipient's email provider"
    Gmail to Outlook Success
    Gmail to Gmail Success

    Considering the result above, I would highly doubt the emails were "rejected by recipient's email provider". I would rather believe they did not pass the Outlook's spam check before sending out.

    17 people found this answer helpful.

  3. Hossein 65 Reputation points

    It's 6th of November 2023 at 11:51 CET and me and all of my collogues in Europe who are using Outlook/Hotmail are facing the same issue.

    It is really annoying and i am using Gmail for now.

    12 people found this answer helpful.

  4. Annette Hall 70 Reputation points

    I found this Microsoft health status website and I believe the Outlook issues are related:

    7 people found this answer helpful.

  5. ALAN 35 Reputation points

    Another workaround for everyone while the problem persists. Set up you email and attachments via the browser outlook. Save to drafts. Then send it from phone app. That also works.

    6 people found this answer helpful.