----- Original Message ----- > From: "Dave Crocker" <dcrocker@xxxxxxxxx> > To: "Franck Martin" <franck@xxxxxxxxxxxxxxx>, "Terry Zink" <tzink@xxxxxxxxxxxxxxxxxxxxxx> > Cc: dmarc@xxxxxxxx, "Ted Lemon" <mellon@xxxxxxxxx>, "IETF" <ietf@xxxxxxxx> > Sent: Monday, November 7, 2016 2:46:54 PM > Subject: Re: [dmarc-ietf] Identification of an email author (was - Re: IETF Mailing Lists and DMARC) > On 11/7/2016 11:41 AM, Franck Martin wrote: >> The EAI WG found it was fine to remove the obligation to have an email >> address part in the mandatory RFC5322.From header, leaving only the >> display part to assert the original author. > > We had that relaxed permission for From:, in the original > From/Sender/Reply-to specification of rfc733, with the requirement that > there be a Sender: email address. It looks like we removed it for rfc822. > > And while I recall something of the EAI discussion, I'm not recalling > this permission's being returned. Nor am I finding it in rfc6854: > > https://tools.ietf.org/html/rfc6854#section-2 > > So, please point to the formal specification that permits a From: field > to have no email address. > I'm not great at ABNF, so please bear with me. My understanding is that RFC proposes the following change: from = "From:" mailbox-list CRLF TO from = "From:" (mailbox-list / address-list) CRLF They are defined by: mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list address-list = (address *("," address)) / obs-addr-list furthermore: address = mailbox / group mailbox = name-addr / addr-spec name-addr = [display-name] angle-addr angle-addr = [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr group = display-name ":" [group-list] ";" [CFWS] display-name = phrase mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list address-list = (address *("," address)) / obs-addr-list group-list = mailbox-list / CFWS / obs-group-list So if you follow the fact that the new from can contain an address list, and that an address can be either a mailbox or a group and that a group can be 'undisclosed sender:;' So you could find an email with the following header From: undisclosed sender:; and that would be ok as per rfc6854 Note the security consideration in same RFC that "discourages" the use of the group syntax, but as a receiver, I would claim, this increases the level of secret sauce to apply to evaluate an email...