This plugin sets various SMTP parameters because several checks need to use a third-party host/domain name in order to work properly. The checks that rely on this are SMTP or DNS relay checks. By default, 'example.edu' is being used for this purpose. However, under some circumstances, this may leak packets from your network to this domain, thus compromising the privacy of your tests. While the owner of example.edu is not known to keep logs of such packet traces, you may want to change this value to maximize your privacy. Note that you absolutely need this option to be set to a third-party domain. This means a domain that has nothing to do with the domain name of the network you are testing.