Microsoft Exchange Online to End Support for SMTP AUTH Basic Authentication

Microsoft announced an updated deprecation roadmap for SMTP AUTH Basic Authentication in Exchange Online: it will continue to function without change through December 2026, be turned off by default for existing tenants at the end of December 2026 (with a temporary re-enable option for continuity), and be permanently removed with a final date to be announced in H2 2027. The advisory highlights security risks of basic authentication (credential theft, lack of MFA enforcement), recommends migration to OAuth or alternative Microsoft services, and urges administrators to inventory SMTP usage and plan migrations using the Exchange admin center visibility tools.