Microsoft 365 Error Codes

Fix Office.com and Teams Error 403 on a BGP Network

Partner Editor Oct 9, 2026 869 views

Question details

Users are experiencing access blocks when attempting to use Microsoft 365 services over a specific network setup.

Fix Office.com and Teams Error 403 on a BGP Network

Product: Microsoft 365 (Office.com and Teams)
Device & OS: not provided
Scenario: Accessing Microsoft 365 services through a BGP network utilizing multiple ISPs.
Observed behavior: Office.com and Teams return a Request Blocked or Error 403 message on the BGP network, whereas the same services function correctly through a standard broadband provider.

Before you start

Ensure you have administrator access to your organization's Microsoft 365 admin center and network configuration, as resolving this requires reviewing routing and endpoint allowlists.

Solution 1Recommended

Review Network Paths and Allow Microsoft 365 Endpoints

Verify that your public IP, proxy, or firewall isn't misclassifying or blocking Microsoft 365 services on your BGP network.

This behavior usually indicates that Microsoft's security filters or your own network infrastructure are blocking the specific routing path. Identifying the difference between your working broadband path and the failing BGP path is crucial.

Identify network paths

Ask your IT administrator to compare the routing path of the failing BGP network with the working broadband connection.

Consult Microsoft documentation

Review the official Microsoft 365 IP Address and URL Web Service documentation to identify all necessary connection points.

Allow required endpoints

Ensure that all required Microsoft 365 URLs and IP addresses are explicitly whitelisted in your firewall, proxy, and BGP routing configurations.

Review Network Paths and Allow Microsoft 365 Endpoints

Administrator Privileges Required: Standard users cannot perform these network checks. You must contact your IT department or network administrator to configure these settings.

Solution 2

Open a Support Ticket with Microsoft

If endpoint whitelisting does not resolve the 403 error, request direct assistance from Microsoft Support to investigate IP blocks.

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Frequently Asked Questions

Why do I get an Error 403 on my BGP network but not on a standard broadband connection?

Microsoft's security filters might misclassify the public IP address or routing path used by your specific BGP network, treating it as unauthorized or suspicious access. Standard broadband IPs are usually recognized as typical user traffic and pass through without issue.

Where can administrators find the required Microsoft 365 IP addresses and URLs?

Administrators can find the comprehensive list by searching for the official 'Microsoft 365 URLs and IP address ranges' documentation provided by Microsoft, which is updated regularly to reflect service changes.

Can a standard user fix the Error 403 on Office.com and Teams?

Typically, no. Because this error occurs on a specific network configuration, it requires network administrators to adjust advanced routing, proxy, or firewall settings and potentially contact Microsoft Support to unblock the IP address.

Microsoft Office Error Codes