Send & Receive Issues

How to Fix Microsoft 365 Sending IPs on SpamCop Blacklist

Tauseeq Magsi Oct 9, 2026 869 views

Question details

Users are experiencing email delivery failures because the shared Microsoft 365 outbound IP addresses they use have been added to the SpamCop blacklist.

What to Do When Microsoft 365 Sending IPs Are on the SpamCop Blacklist

Product: Microsoft 365
Device & OS: not provided
Scenario: Sending legitimate outbound emails to external recipients and receiving bounce-back messages due to sender IP blacklisting.
Observed behavior: Emails fail to deliver, returning Non-Delivery Reports (NDRs) indicating that the receiving server rejected the message because the Microsoft 365 sending IP is listed on SpamCop.

Before you start

Verify your email delivery failure by checking the Non-Delivery Report (NDR) bounce message to confirm that SpamCop is specifically citing the Microsoft sending IP address as the reason for rejection.

Solution 1Recommended

Report Delivery Failures to Microsoft Support

Since the blocked IP belongs to Microsoft's shared infrastructure, you must escalate the issue to Microsoft so they can investigate the abuse and work with SpamCop to delist the IP.

Microsoft 365 uses a shared outbound email infrastructure. This means many organizations, including trial accounts, share the same sending IP addresses. If one account sends spam or gets compromised, the shared IP may be blacklisted. Customers cannot delist these IPs themselves; Microsoft's engineering team must resolve the reputation problem directly with the blacklist provider.

Collect NDR Messages

Gather the specific Non-Delivery Reports (NDRs) or bounce messages you received. Note the exact IP address and the error code indicating the SpamCop block.

Access the Admin Center

Open a Support Request

Navigate to the 'Support' section and click 'New service request'. Briefly explain that a Microsoft outbound IP is blacklisted by SpamCop and provide the NDRs as evidence.

Wait for Microsoft Investigation

Allow Microsoft support to investigate the source of the abuse on their network and submit the delisting request to SpamCop.

Report Delivery Failures to Microsoft Support

Resolution Time: Delisting shared IPs can take time depending on Microsoft's investigation into the abusive tenant. It is highly recommended to follow up on your support ticket regularly.

Solution 2

Contact the Receiving Organization's IT Administrator

Ask the recipient's IT department to adjust their filtering logic to allow your emails through, rather than relying solely on strict IP-based blocklists for shared infrastructures.

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Frequently Asked Questions

Can I remove the Microsoft 365 IP address from SpamCop myself?

No, customers generally cannot delist a Microsoft-owned outbound IP address themselves. Because the IP is part of Microsoft's shared infrastructure, Microsoft must investigate the root cause of the abuse and work directly with SpamCop to resolve the listing.

Why did a Microsoft 365 IP get listed on SpamCop in the first place?

Microsoft 365 uses shared outbound email infrastructure. An IP address can get blacklisted if it is heavily used by compromised accounts, abused by trial accounts sending spam, or due to inaccurate reporting to SpamCop's automated system.

How can receiving servers prevent blocking legitimate Microsoft 365 emails?

Receiving organizations are encouraged to use reputable, validated blocklists and sophisticated spam filtering mechanisms instead of automatically blocking entire subnets or shared IP addresses that host thousands of legitimate domains.

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