While it is possible to run the ESA without DNS access, it is not recommended or supported. A configuration without DNS is difficult to set up and would disable access to valuable features. For example, SenderBase scores would be unavailable, and no domain information would be included in the logs or Reporting. In this case, all configurations would have to be entered as IP addresses and a proxy server may be needed to retrieve updates. In order to deliver to the Internet in general, another server that does have DNS access would have to act as a gateway for the ESA. This type of configuration would limit the ESA to applications where mail is only flowing to a few servers and the ESA is simply used to perform content scanning.