Email property is empty on SPUser object, how to fill?

Question

I have a piece of code which gets the email address of a SPUser object. The email property is empty. Where I can fill the email address of this user? Is it in SharePoint or somewhere in AD? I dont have a sync connection to AD!

SPFieldUser userField = (SPFieldUser)currentItem.Fields.GetField(Constants.Fields.FIELD_CLIENT);
            SPFieldUserValue fieldValue = (SPFieldUserValue)userField.GetFieldValue(Convert.ToString(currentItem[Constants.Fields.FIELD_CLIENT]));
            SPUser assignedToUser = fieldValue.User;


string clientEmail = assignedToUser.Email;

// dosomething

Answer 1

You will need to actually request the user profile for that user so you can read all the properties for that user (including email). This question has some samples of how to do that in code: How to get user profile property value when privacy for property set to "Private" (only me)