UFN_EXCHANGEINTEGRATION_VALIDAPPUSER

            create function dbo.UFN_EXCHANGEINTEGRATION_VALIDAPPUSER
            ( 
                @APPUSERNAME nvarchar(128)
            )
            returns bit
            with execute as caller
            as
            begin
                declare @VALID bit
                set @VALID = 0

                if exists(select ID from dbo.APPUSER where APPUSER.USERNAME = @APPUSERNAME) begin
                    set @VALID = 1
                end

                return @VALID
            end