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)>'

Question

Hello,

I am currently experiencing an issue where my outgoing emails are being rejected. The error message I receive is as follows:

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)>'

This is typically followed by a lengthy diagnostic message.

I have already contacted Microsoft Support; however, they were unable to resolve the issue and advised me to reach out to Outlook Support.

To troubleshoot, I have taken the following steps:

• Changed the email format to Plain Text
• Sent a test email to myself (unsuccessful)
• Sent test emails to multiple external email addresses (all rejected)
• Attempted to send emails via the web browser version (same issue)
• Tested across different Outlook applications and devices (issue persists)
• Emails to Gmail / Yahoo / Various Business & Personal emails - All rejected.

Despite these efforts, I am still unable to send emails, and the problem remains unresolved. This has become quite frustrating, and I would greatly appreciate any help and assistance.

Thanks

-Katie

Answer 1

Dear Katie @CBSkips, 

Thank you for the detailed description. Could you please let me know if this issue has been resolved for you yet? 

If you are still experiencing this, I want to note that the troubleshooting steps you took were excellent and very thorough. Based on your description and the specific error message, it is highly likely that the account itself is rate-limited or reputation-blocked at the service level. 

Usually, the best course of action for this type of block is to simply wait for an auto-unblock, as the system often resets these restrictions automatically after a period of time. If waiting does not clear the restriction, I advise you to contact Outlook Support directly and ask for a manual reputation review and unblock.

You can reach them by following these steps: 

1. Sign in to Outlook.com from a web browser. 
2. Click on the Help icon (the question mark) at the top right of the page. 
3. Type your issue in the search box and press Enter. 
4. Scroll down to "Still need help?" and select Yes. 
5. Follow the prompts to connect with a support advocate who can look into your account's sending reputation. 

Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas only. 

I hope these steps help you get your emails flowing again. Feel free to let us know the results, I’ll be happy to guide you further and make sure you get this sorted out. 

---

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

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread. 

Answer 2

The error 550 5.7.520 Message blocked because it contains content identified as spam. AS(4810) indicates that outgoing messages are being blocked because the sending IP or message content is currently treated as spam by Outlook.com/Hotmail.

For Outlook.com senders, the documented steps to improve spam reputation and restore normal sending are:

1. If anti‑virus software is installed, locate and turn off any feature named Internet Email Auto Protect or Internet Email Protection, then send a test message again.
2. Ensure the account has a clear, identifiable display name on outgoing email so the “send as” identity is easily recognized. Instructions for changing the “send from” address and name are in Outlook.com.
3. Send an email to the same Outlook.com account (self‑send), open that message, and reply to it. This can help establish normal interaction patterns.
4. Add trusted correspondents to the Contacts list so that their messages and replies are treated as legitimate. Steps for managing contacts in Outlook.com are in Create, view, and edit contacts and contact lists in Outlook.com.

If delivery failures continue after these actions, use the guidance under “Failed delivery messages from the postmaster at outlook.com, microsoft.com, or service.microsoft.com” in the same article to review the full NDR and follow any additional remediation steps provided there.

---

References:

• Sender Support in Outlook.com