Network Heretics Oracle This document defines several mechanisms which can be used by a client such as a Mail User Agent or Mail Submission Agent, to query an SMTP server which is configured to accept incoming mail for a mail domain, to obtain information associated with an email address based in that domain. Among other purposes, these mechanisms are intended to facilitate discovery of senders' and/or recipients' public keys for use in automatic verification of whole-message digital signatures and automatic whole-message encryption of email sent to recipients.