B2B Invitation Redemption Flow

The invitation redemption process occurs when a guest user follows a link in an email or uses a direct link to access a resource. If a user lacks a Microsoft account, email one-time passcodes (OTP) serve as a fallback authentication method to ensure access. Successful redemption creates a guest user object in the directory, typically identified by a unique User Principal Name (UPN) format containing the "#EXT#" identifier. Troubleshooting often involves checking allowlists or blocklists in the external collaboration settings to ensure the user's domain is permitted.