UFN_EXCHANGESERVER_DEFAULTSERVERCOUNTVALID

            create function dbo.UFN_EXCHANGESERVER_DEFAULTSERVERCOUNTVALID()        
            returns bit
            with execute as caller
            as
            begin
                declare @VALID bit
                set @VALID = 1

                if (select count(ID) from dbo.EXCHANGESERVER where EXCHANGESERVER.ISDEFAULTSERVER = 1) > 1 begin
                    set @VALID = 0
                end

                return @VALID
            end