Generally speaking, service providers use the NameID attribute as the user's identity. By default, the user's login name is returned in the NameID.
In the DualShield Admin Console, find the Service Provider, e.g. "ADFS".
In the context menu of the service provider, select "Edit"
Change the "NameID Format" to "Map to the following attribute"
Select "email" as the "Attribute"
Click Save