I don't think it's just about SSO. Exchange isn't cheap to license or keep operational. If you switch to exchange in cloud it doesn't reduce the costs that much

I don't think it's just about SSO. Exchange isn't cheap to license or keep operational. If you switch to exchange in cloud it doesn't reduce the costs that much. Hopefully soon Microsoft will realize the value some of their products (SQL Server and Exchange) isn't nearly what it used to be and that they need to adjust prices and licensing requirements.