Legacy SharePoint Invitation Manager is being retired

Updated January 24, 2024: We have added additional information regarding this change. We are completing our retirement of the legacy SharePoint Invitation Manager for guests. This platform is currently used only when Document Libraries are shared externally or when an external user is shared to with a custom role. These flows will now use Entra B2B Invitation Manager instead. [When this will happen:] Targeted Release: We will begin rolling out early December 2023. Standard Release: We will begin rolling out early January 2024 and conclude by late February 2024. [How this will affect your organization:] We are completing our retirement of the legacy SharePoint Invitation Manager for guests. This platform is current used only when Document Libraries are shared externally or when an external user is shared to with a custom role. These flows will now use Entra B2B Invitation Manager instead. This means that these flows will now also respect any policies or settings in the Entra B2B admin center.  Note: The primary Entra & ODSP settings that need to be consistent are the Allow/Deny domains policy and the "Who Can Share"/"Guest Inviter" role policies. If these policies are not inline, it may result in failures during the sharing flow (for example, SPO allows sharing to outlook.com but Entra blocks sharing to outlook.com) This change is unaffected by the "EnableAzureADB2BIntegration" setting in SPO PowerShell. This setting only applies to file/folder sharing. This change only applies to a very small set of legacy sharing actions, including sharing of document libraries and sharing via custom roles. All other flows (File/folder sharing, site sharing) will continue to use the previous & selected behaviors. [What you need to do to prepare:] You may need to update your documentation for end users. You should also check your Entra B2B settings to ensure they are consistent with policies in the SharePoint Admin Center.