Subject: Re: [ietf-822] Update to RFC 5322 to allow "group" syntax in the "from" header

From: "John R Levine" <[email-masked]>
Date: 2 Aug 2012 10:39:45 -0700

Executive summary: I sent myself some messages with an empty group in 
From: headers to see what various MUAs did with them.  Nothing broke.

* Alpine (my normal client)

Displayed OK.  Invented a matching Reply-To: line.  If I reply, the To: 
line is empty.

* Thunderbird

Displayed OK. Reply put the same empty From: group on the To: line, 
rejects attempts to send it with a message saying to fix the To: line.

* Evolution

Displayed OK. Reply has a blank To: line.

* Android mail

Displayed OK. Reply has a blank To: line.

* Squirrelmail (popular webmail IMAP client)

Displayed OK, reply put the null group on the To: line and let you try
to send mail to it.

* Yahoo Mail

Filed as spam but displayed reasonably.  Reply had an empty To: line.

* Gmail

Filed as spam but displayed reasonably.  Reply had an empty To: line.

* Hotmail aka outlook.com

Displayed OK. Reply put the same empty From: group on the To: line, 
rejects attempts to send it with a message saying to fix the To: line.

-----------------------------------

Here's the message.

Date: Thu, 2 Aug 2012 09:24:15
From: A foreign person:  ;
To: <various addresses>
Subject: let's have lunch

at the sushi place at 1230

Regards,

---

From: Mark Martinec <[email-masked]>
Date: Wed, 8 Aug 2012 16:40:58 +0200

John R Levine wrote:
> [...]

Ditto for kmail 1.13.7 (KDE 4.8.4).
  (although kmail misparses (but survives) the more complex example
  in RFC 5322 Appendix A.5 - but that is another story)

Also tested a content filter Amavis, it parses the address-list syntax
in a From header field correctly, including the RFC 5322 A.5 example.

Hector Santos wrote:
> Currently, I am pretty sure our software will not break, but if a 
> group address is added to From:, that will became part of the id 
> (display name). That will make the first address id "A Group:Ed Jones"

Semantically a group name behaves as a display name, so
in some generalized meaning I don't find it incorrect
to concatenate a group (display) name to every display
name in its group-list.

One comment on the change:

-   In either case, an optional reply-to field MAY also
-   be included, which contains the field name "Reply-To" and a comma-
-   separated list of one or more addresses.
+   In either case, an optional reply-to field MAY also
+   be included, which contains the field name "Reply-To" and a comma-
+   separated list of one or more addresses (either mailbox or group
+   syntax).

I think the original statement should be left alone,
the document shouldn't be touching a "Reply-To" semantics,
which I already find problematic (what's the point in having
a group with an empty list of mailboxes in a Reply-To ?)

There is one concern that I have. A "Sender" field was supposed
to be required when a "From" does not contain exactly one
mailbox name. With relaxed syntax allowing "address-list"
in a "From" header field, and with "group" syntax allowing
an empty "group-list", the draft seems to count a "group"
as one address, even if its "group-list" is empty.

I think the requirement for the presence of a "Sender" field
should depend on the number of "mailboxes" (instead of "addresses")
not being exactly one, i.e. not counting a group as exactly
one address, but counting mailboxes in its "group-list".
Otherwise the purpose of requiring a Sender (when it can't
be uniquely derived from a "From" field) seems to be lost.

In other words, I think the "Sender" should be required
when a "From" header field specifies a group with an empty
list of mailboxes.

  Mark

---

From: "John Levine" <[email-masked]>
Date: 8 Aug 2012 21:30:25 -0000

>when a "From" header field specifies a group with an empty

This is a reasonable suggestion, except that the primary motivation
for this change is EAI messages downgraded by POP or IMAP delivery
agents.  If the addresses on the From: or Reply-To: line are
non-ASCII, there is no way for an ASCII MUA to display or reply to
them, so the idea is that the header will be rewritten to something
like this:

  From: an international address :;

So either there's an existing Sender header, which might itself need
to be downgraded, or there isn't, but either way there's no promise
that there is a non-ASCII address that could be put in the Sender.
So it's not gonna happen.

R's,
John

PS: EAI went around for years trying to come up with a general way to
allow non-ASCII mail software to read and reply to EAI messages, and
finally gave up.  See the experimental RFCs and the mailing list for
details.

-- 
Regards,
John Levine, [email-masked], Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. http://jl.ly

---

From: "John Levine" <[email-masked]>
Date: 8 Aug 2012 21:33:32 -0000

The sender and resent-sender headers have the same issue on downgrade.  The current syntax
says they contain a mailbox.

I suppose that since they're optional a downgrade could just delete
them, but if we're allowing null groups in From, how about null groups
in Sender and Resent-Sender, too?

R's,
John

---

From: Keith Moore <[email-masked]>
Date: Wed, 08 Aug 2012 17:42:11 -0400

I intensely dislike what EAI has done to email interoperability, and I 
don't think that IETF should have ever standardized email addresses that 
wouldn't work with legacy mail processing software.

Having said that, there's been a longstanding need for a non-replyable 
originator address in a wide variety of situations.   I'm not 
particularly enamored with the idea of using group syntax to represent 
such an address, but it might be better than some of the alternatives.

Keith

---

From: Ned Freed <[email-masked]>
Date: Wed, 08 Aug 2012 18:40:14 -0700 (PDT)

> in Sender and Resent-Sender, too?

+1

				Ned

---

From: Barry Leiba <[email-masked]>
Date: Thu, 9 Aug 2012 00:10:50 -0400

> a group with an empty list of mailboxes in a Reply-To ?)

This is actually a clarification: Reply-To already allows either
mailbox or group syntax (in the ABNF), and I just thought it a good
idea, while I was touching that text, to make it clear in the text.

Barry

---

From: Barry Leiba <[email-masked]>
Date: Thu, 9 Aug 2012 00:13:21 -0400

> The sender and resent-sender headers have the same issue on
> downgrade.  The current syntax says they contain a mailbox.
>

I need to go dig back and see why the issue only came up with From,
and not with Sender.  If it's an oversight, then you're right.  In any
case, conceptually, there's no reason why the "sender" of the message
couldn't be a group.

And just to clarify, this change is not just allowing *null* groups:
it's a change to allow *any* groups at all, null or otherwise.

Barry

---

From: "John R Levine" <[email-masked]>
Date: 9 Aug 2012 00:32:47 -0400

> it's a change to allow *any* groups at all, null or otherwise.

In From lines that makes sense since they're allowed to have multiple 
mailboxes.  Sender lines currently can only have a single mailbox, so I'd 
think that if we allow groups, they should allow only 0 or 1 mailboxes.

Regards,
John Levine, [email-masked], Taughannock Networks, Trumansburg NY
"I dropped the toothpaste", said Tom, crestfallenly.