Send & Receive Issues

How to Request an IP Exception for Exchange Online Email Blocking (Error 550 5.7.708)

Tauseeq Magsi Oct 16, 2026 868 views

Question details

Users need to resolve SMTP error 550 5.7.708 caused by an IP address with a low reputation being blocked by Exchange Online.

How to Request an IP Exception for Exchange Online Email Blocking

Product: Microsoft 365 Exchange Online
Device & OS: not provided
Scenario: Sending emails from a Microsoft 365 Developer tenant or an IP address that has developed a low reputation.
Observed behavior: Emails fail to send entirely, and the server returns SMTP error 550 5.7.708 indicating the sending IP address is blocked.

Before you start

Ensure you have the exact blocked IP address ready and verify that you have administrator access to the Microsoft 365 admin center, as standard users cannot submit service requests for IP exceptions.

Solution 1Recommended

Submit a Delisting Request via the Microsoft Anti-Spam Portal

The quickest way to remove your IP from the Microsoft blocklist is to use the automated delisting portal.

Microsoft maintains an automated portal where users can request their IP addresses to be removed from the blocked senders list. This is the first step you should take when encountering error 550 5.7.708.

Access the Delist Portal

Open a web browser and navigate to the Microsoft anti-spam IP delist portal at sender.office.com.

Enter IP and Email Information

Enter the email address you are using to send the request and the specific IP address that is currently blocked.

Submit the Request

Complete the CAPTCHA verification on the page and click the 'Submit' button.

Confirm Your Email

Check your email inbox for a confirmation link sent by Microsoft. Follow the instructions in the email to confirm your address.

Finalize Delisting

Click 'Delist IP' in the confirmation portal. Please allow up to 24 hours for the unblocking changes to propagate globally across all Exchange Online servers.

Submit a Delisting Request via the Microsoft Anti-Spam Portal

Propagation Time: While the request is processed quickly, it can take up to 24 hours for email delivery to fully return to normal.

Solution 2

Create a Service Request in the Microsoft 365 Admin Center

If the automated delisting portal fails or the block persists after 24 hours, an administrator must create a direct service ticket.

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Frequently Asked Questions

How long does it take for a Microsoft IP delisting request to take effect?

Once you submit a delisting request through sender.office.com and confirm it via email, it typically takes up to 24 hours for the IP block to be fully lifted and for email delivery to return to normal.

Why am I getting SMTP error 550 5.7.708?

This error is triggered when your sending IP address has developed a low reputation in Microsoft's systems. This is particularly common for new Microsoft 365 Developer tenants or if the IP address was recently associated with sending spam or unauthorized bulk emails.

Can a standard user request an IP exception in Microsoft 365?

Standard users can attempt to use the automated delisting portal at sender.office.com. However, if the issue persists and requires a manual IP exception via a service ticket, only a Microsoft 365 tenant administrator can log in to the admin center to submit the request.

What should I do if my IP is blocked again after delisting?

If your IP is repeatedly blocked, check your outbound email traffic for compromised user accounts, malware, or bulk mailing behavior violating terms of service. Once you have resolved the underlying security issue, contact Microsoft Support via the admin center to explain the remediation steps you have taken.

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