Outlook.com blocks all outbound messages with 550 5.7.520 AS(4810), including replies to Microsoft Support

Question

Outlook.com blocks all outbound messages with 550 5.7.520 AS(4810), including replies to Microsoft Support

Phishing Report 0

My personal Outlook.com account rejects legitimate outgoing messages with:

550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)

The restriction also blocks short plain-text replies to an existing official Microsoft Support thread, even without links or attachments.

I have verified the recovery information and checked recent account activity. Microsoft Support confirmed that the problem may be related to account reputation, but the recommended steps did not resolve it.

Filtering correlation IDs:

591f53ad-c761-46a7-ba8a-08df0bafabdb

3519ceb6-f09f-445b-a4a6-08df0c207d5d

How can I request a manual technical review of this false-positive AS(4810) restriction? Which Microsoft team can examine these correlation IDs if Outlook blocks replies to the existing support case?

I can provide the full non-delivery reports and support case number privately to an authorized Microsoft representative.

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Ответы: 2

Ваш ответ

Answer 1

SD - IA 180.3K Независимый помощник

Hi,

This is a very common error, most commonly due to IP reputation. Please restart the router once to get a new IP address, which solves it often.

Do not use a signature in the email as it directly tells Microsoft systems that it might be spam.

try switching the Email to Plain Text instead of HTML as a troubleshooting step to verify.

The setting is below:

Open the Gear icon > Settings.
Go to Mail > Compose and Reply.
Change the message format to Plain text.

User's image

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

Phishing Report 0 Баллы репутации

2026-09-06T15:36:18.5066667+00:00

Thank you for the suggestions.

I changed the default message format to Plain text and sent another test without a signature. The message contained only one ZIP attachment under 3 MB, with no nested archives.

Unfortunately, Outlook rejected it again with the same error:

550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)

The latest filtering correlation ID is:

8a3d53d8-1e03-49d7-31c8-08df0c2c1bb1

This test confirms that the HTML format and signature were not the cause. Could you please advise how I can request a manual account-reputation review or escalate these correlation IDs to the Outlook.com outbound filtering team?

Answer 2

SD - IA 180.3K Независимый помощник

Thank you, did it go through without attachment?

Please file a problem report at https://sender.office.com for the next steps. It will take 48 hours and the problem will be solved.

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