code: def expand_dl(opts)
        opts = opts.clone
        req = build_soap! do |type, builder|
          if(type == :header)
          else
          builder.nbuild.ExpandDL {|x|
            x.parent.default_namespace = @default_ns
            x.Mailbox {|mb|
              key = :email_address
              mb[NS_EWS_TYPES].EmailAddress(opts[key]) if opts[key]
              builder.item_id! if opts[:item_id]
            }
          }
          end
        end
        do_soap_request(req)
      end
docs: ------------ Utility Operations ------------
   Exposes the full membership of distribution lists.
   @see http://msdn.microsoft.com/en-us/library/aa494152.aspx ExpandDL
  
   @todo Fully support all of the ExpandDL operations. Today it just supports
     taking an e-mail address as an argument
   @param [Hash] opts
   @option opts [String] :email_address The e-mail address of the
     distribution to resolve
   @option opts [Hash] :item_id The ItemId of the private distribution to resolve.
     {:id => 'my id'}