RFC 5321, "Simple Mail Transfer Protocol", October 2008Source of RFC: IETF - NON WORKING GROUP
Area Assignment: app
Errata ID: 4055
Reported By: Dave Crocker
Date Reported: 2014-07-19
Rejected by: Barry Leiba
Date Rejected: 2014-07-19
Section 3.6.2 says:
This specification does not deal with the verification of return paths for use in delivery notifications. Recent work, such as that on SPF  and DKIM  , has been done to provide ways to ascertain that an address is valid or belongs to the person who actually sent the message.
It should say:
This specification does not deal with the verification of return paths for use in delivery notifications.
Neither SPF nor DKIM determine "validity" of an address. SPF determines whether an IP Address is 'authorized' to send mail with a particular domain name in the return address, but that does not validate the entire address, nevermind validating any destination or author addresses. DKIM has nothing at all to do with any existing address or domain name elsewhere in the message.
So I suggest merely dropping the problematic sentence.
This is a change request, not an errata report.