Not able to send email - has been temporarily rate limited due to IP reputation

Question

I am getting the following error message when trying to send to a couple of hotmail/outlook emails. I have been able to send without issue in the past:

host outlook-com.olc.protection.outlook.com[[Moderator note: personal info removed]]

    said: 451 4.7.650 The mail server [Moderator note: personal info removed] has been temporarily rate

    limited due to IP reputation. For e-mail delivery information, see

    https://aka.ms/postmaster (S775) [Name=Protocol Filter

    Agent][AGT=PFA] [Moderator note: personal info removed]

    [Moderator note: personal info removed].namprd04.prod.outlook.com 2026-02-17T05:01:23.138Z

   (in reply to MAIL FROM command)

I do send emails frequently as they are directors emails. The outlook that has bounced is only emailed occasionally. The Hotmail email is sent to daily.

Answer 1

Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data.

Hi @Mark Bennett

Thank you for posting your question in the Microsoft Q&A forum. 

First, I’d like to clarify that this is a user‑to‑user support forum. Moderators, contributors, and external Microsoft employees participating here do not have access to backend systems, nor can we directly intervene in Microsoft product features. Our role is limited to providing technical guidance and sharing best practices based on reported issues, requests, or ideas.

I found an article that might help with your case: How to resolve Microsoft 451 4.7.650 error during email IP warm-up? - Sender reputation - Email del…

Note: This information is provided as a convenience to you. These sites are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please ensure that you fully understand the risks before using any suggestions from the above link.

First, you need to understand this 451 4.7.650 error is just a temporary block. It indicates Microsoft's systems have detected something suspicious about your IP's sending behavior. Some of the factors that might trigger this include the volume of emails you have sent, recipient engagement or content.

If this IP belongs to your organization, please use https://olcsupport.office.com/ to delist your IP. If you are not the IT admin, please raise this concern to them, they will be able to file a support request.

Additionally, if you are using Microsoft 365 services, you can submit a support ticket through the Admin Center. A Microsoft support agent will be able to assist you directly and provide more authoritative information.

Currently, Microsoft does not offer any native tool to check IP health and reputation, you can consider using third-party IP address reputation checker. Third party tools are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability. Please ensure that you fully understand the risks before using it.

I hope this information helps.

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Answer 2

Can you please tell me how to check ip reputation

Answer 3

The error message you are encountering indicates that your IP address has been temporarily rate limited due to its reputation. This typically happens when suspicious activity is detected from the source IP address, leading to a restriction on sending emails until the situation is evaluated.

To resolve this issue, you can take the following steps:

1. Wait for the restriction to be lifted: Microsoft will evaluate the traffic from your IP address, and if everything is deemed okay, the restriction will be removed.
2. Check your IP reputation: You can use tools like the Microsoft Postmaster to check the reputation of your IP address and understand any issues that might be affecting it.
3. Follow best practices for email sending: Ensure that you are following best practices for email deliverability, such as maintaining a clean mailing list and avoiding spam complaints, which can negatively impact your IP reputation.
4. Contact support if needed: If the issue persists, consider reaching out to Microsoft support for further assistance.

By addressing the underlying issues with your IP reputation, you should be able to resume sending emails without encountering this error.