in region routing

In region routing for Microsoft 365 Multi-Geo deployments reached General Availability in December 2025, giving administrators control over where inbound email enters Exchange Online for geographically distributed users. This feature alters the inbound mail entry point for anonymous and hybrid mail, maps accepted domains to geo regions, and can prevent cross-geography transit for incoming SMTP sessions. For multinational organizations dealing with data residency rules, regulatory audits, or internal sovereignty mandates, in region routing provides a practical tool to enforce compliance and optimize mail flow.