Adding Organizations with Modern Authentication and Legacy Protocols
When you add an organization using the modern authentication method with legacy protocols allowed, you can use either a user account or an Azure AD application for authentication. Veeam Backup for Microsoft Office 365 uses a user account or an application to establish a connection to your Office 365 organizations with disabled security defaults and maintain data transfer during backup and restore sessions.
To add a new Microsoft Office 365 organization, check prerequisites and do the following: