Important Update: Server Name Indication (SNI) Now Mandatory for Azure DevOps Services

This post announces the mandatory requirement of Server Name Indication (SNI) for all incoming HTTPS connections to Azure DevOps Services, effective April 23rd, 2025. It explains SNI's role in TLS protocol for hostname specification, notes that most modern clients are SNI-ready, but highlights potential compatibility issues with outdated software, proxies, or firewalls. The post provides detailed instructions for testing SNI compatibility using PowerShell, curl, browsers, and host file overrides, and lists common error messages associated with SNI issues.