Does Verify Addresses reliably report VALID DOMAIN vs. INVALID DOMAIN?
Yes for VALID DOMAIN, no for INVALID DOMAIN. Domains are detected using the DNS (Domain Name Server) service. All VALID DOMAIN reports should be 100% accurate, there should be no “false positives”. But DNS simply times out and doesn’t report anything for invalid domains. Most of the time an invalid domain is really an invalid domain, but sometimes they turn out to be temporarily “off the air”, or taking an exceptionally long time to respond, or the domain is too new, or for some other reason the domain is unknown to your DNS server, or the DNS server was just too busy to respond (DNS is a “UDP” Internet protocol, which means that dropped requests are to be expected). The Verify Addresses command does perform DNS retries, but often what is required is retrying a number of minutes later. Hence, some INVALID DOMAIN reports are occasionally “false negatives”. Therefore, it is usually worth re-verifying INVALID DOMAIN addresses at a later time before concluding that they are really bogus.
