VSTS will no longer allow creation of new MSA users with custom domain names backed by AzureAD

This post announces the deprecation of new Microsoft Account (MSA) sign-ins with custom domain names backed by Azure Active Directory (Azure AD) for Visual Studio Team Services (VSTS). It explains the rationale behind this change, highlighting the lack of central governance for personal MSA accounts and recommending the use of Azure AD accounts for organizational control. The post provides a deadline (March 30th, 2018, later extended to September 2018) and outlines recommended actions for users, primarily connecting their VSTS account to an Azure AD tenant and ensuring all users are members or guests of that tenant.