1. IANA Considerations
As directed by SMTP , IANA maintains a registry  of “WITH protocol types” for use in the “with” clause of the Received header in an Internet message. This registry presently includes SMTP , and ESMTP . This specification updates the registry as follows:
o The new keyword “ESMTPA” indicates the use of ESMTP when the SMTP AUTH  extension is also used and authentication is successfully achieved.
o The new keyword “ESMTPS” indicates the use of ESMTP when STARTTLS  is also successfully negotiated to provide a strong transport encryption layer.
o The new keyword “ESMTPSA” indicates the use of ESMTP when both STARTTLS and SMTP AUTH are successfully negotiated (the combination of ESMTPS and ESMTPA).