def mx_servers
      return @mx_servers if @mx_servers
      @mx_servers = []
      mx_records.each do |mx|
        @mx_servers.push(preference: mx.preference, address: mx.exchange.to_s)
      end
      @mx_servers
    end
def mx_servers
      return @mx_servers if @mx_servers
      @mx_servers = []
      mx_records.each do |mx|
        @mx_servers.push(preference: mx.preference, address: mx.exchange.to_s)
      end
      @mx_servers
    end
The servers that this domian MX records point at.

 @return [Array<Hash>] Array of type { preference: 1, address: '127.0.0.1' }