Send & Receive Issues

How to Fix Outlook Email Blocked by SpamCop RBL

Adam Davis Sep 30, 2026 868 views

Question details

The user is experiencing email delivery failures when sending messages via Outlook, as the outbound emails are being rejected by external mail servers due to a blocklist.

How to Fix Outlook Email Blocked by a SpamCop RBL

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Sending an email reply to an external client.
Observed behavior: The sent email bounces back with a Non-Delivery Report (NDR) indicating that the Microsoft outbound IP address is listed on the SpamCop RBL.

Before you start

Locate and save the complete Non-Delivery Report (bounce message) you received, as you will need the specific error codes and IP addresses to share privately with IT administrators.

Solution 1Recommended

Contact the Recipient's Email Administrator

Because the recipient's server is enforcing the SpamCop blocklist, their administrator must investigate and manually allow your messages to pass through.

SpamCop RBLs temporarily list IP addresses that have been detected sending spam. Since you are using a shared Microsoft outbound IP, you cannot remove the IP from the list yourself. The most effective workaround is to have the receiving end whitelist your domain.

Notify the recipient through an alternative method

Reach out to the intended recipient via a phone call or a secondary email address to inform them that your emails are bouncing.

Provide the bounce details privately

Forward the complete Non-Delivery Report to the recipient or their IT team, highlighting the exact Microsoft outbound IP address (e.g., 40.107.117.103) that was blocked.

Request domain whitelisting

Ask the recipient's email administrator to add your sending domain or the affected Microsoft IP to their spam filter's safe sender or whitelist configuration.

Contact the Recipient's Email Administrator

Protect Sensitive Information: Never post your complete bounce message publicly on community forums, as it contains sensitive routing data and internal email addresses.

Solution 2

Test Delivery to Other External Recipients

Check if the block is an isolated issue with one specific strict mail server or a broader problem affecting all your outbound emails.

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Frequently Asked Questions

What is a SpamCop RBL and why did it block my email?

A SpamCop RBL (Real-time Blackhole List) is a dynamic database of IP addresses reported for sending spam. Recipient mail servers use it to block suspicious traffic. Your email was blocked because the shared Microsoft outbound server IP you used was temporarily flagged on this list.

Can I manually remove the Microsoft IP address from SpamCop?

No. As an end-user, you cannot delist a Microsoft-owned IP address from an RBL. Microsoft's network administrators actively monitor these lists and handle delisting requests, or the IP is automatically removed once the spam traffic ceases.

Why would a legitimate Microsoft IP be blacklisted?

Because Office 365 handles millions of emails, spammers occasionally compromise valid accounts and send bulk spam through Microsoft's shared outbound servers. This temporarily damages the reputation of the shared IP address, triggering RBL blocks for other legitimate users.

Is it safe to share my email bounce message online to get help?

No, it is highly discouraged. Bounce messages contain sensitive routing information, internal server IP addresses, and private email addresses. You should only share this information privately with the recipient's IT administrator or verified technical support.

Outlook & Email Problems