Relay protection system URL

For Microsoft Exchange Online, the primary relay protection URL is the MX record domain, typically in the format *.mail.protection.outlook.com.

Overview

Relay protection URLs are used to ensure that email traffic is securely routed through authorized servers, preventing unauthorized relaying and spam. In Microsoft Exchange Online Protection (EOP), your organization's MX record points to a domain like company-com.mail.protection.outlook.com, which acts as the relay endpoint for incoming and outgoing emails. Key Points for ConfigurationMX Record Domains: All inbound email should be directed to your organization's MX record domain (e.g., company-com.mail.protection.outlook.com) to ensure proper filtering and relay protection.

Firewall and Proxy Settings: Ensure that your network allows outbound and inbound connections to these domains over standard email ports (SMTP: 25, SMTPS: 587 if used) to avoid delivery issues. Sub-URLs and FQDNs: If your email system or security solution inspects URLs, allow all subdomains under the MX record domain to ensure updates, anti-spam, and anti-malware services function correctly. Hybrid Deployments: For organizations using a hybrid Exchange setup, both on-premises and cloud servers must be able to communicate with the relay protection URLs to maintain seamless mail flow.

Best Practices

Whitelist M

X Domains: Add your MX record domains to firewall and proxy allow lists to prevent blocking legitimate email traffic. Monitor Updates: Microsoft periodically updates IP ranges and endpoints; check the official Microsoft 365 URLs and IP address ranges documentation to stay current. Use Secure Protocols: Always use TLS/SSL for SMTP connections to the relay URLs to maintain secure email transmission.

Test Connectivity: Verify that your email servers can reach the relay protection URLs and that no intermediate firewall or proxy is blocking required ports. By correctly configuring your network to allow these relay protection URLs, you ensure secure, reliable email delivery while maintaining protection against unauthorized relaying and spam.