XFOR: IMC NDRs or Misdirects Mail Without Domain Address

CAUSE

If the SMTP recipient address does not include the "@domain" part of an address, the IMC attempts to resolve a domain name consisting simply of the period (.). If the Domain Name Service (DNS) queries for the domain "." result in an answer, the mail is sent to that SMTP host. The message will eventually be rejected by the receiving host, because the user name does not exist on that erroneous SMTP host. If the DNS queries for domain "." do not result in an answer, the message is re-queued by the IMC for possible delivery later with the reason "Host Unreachable".