a. System.Web.Mail is not supported under version 3.5 of the
Framework.
b. System.Web.Mail is depredcated under version 3.5 of the
Framework, and it is officially recommended that System.Net.Mail be used.
c. System.Web.Mail is the preferred solution when using IIS
hosted applications.
d. There are no functional differences; the items were moved
to a new namespace to better reflect their applicability.