Some versions of Outlook misinterpret mails with only BCC recipients

[David Ayers]

Binary package hint: thunderbird

Mails sent from Thunderbird which merely contain BCC entries generate a TO: header in the de_AT.UTF8 locale like:

To: Verborgene_Empfaenger: ;

This header can be parsed by:
Microsoft Outlook Express 6.00.2900.3664
for example Outlook version:
Microsoft Office Outlook, Build 11.0.5510
does not decode these mails correctly.

The the raw MIME format including all the headers are presented.
I'm not sure whether the To header must contain a valid address,

Evolution warns about an empty To: header invoking an Apparently-To: header on some systems revealing the BCC recipients. Maybe a warning with the suggestion to add the sender as the To: recipient would satisfy both cases.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: thunderbird 3.1.7+build3+nobinonly-0ubuntu0.10.04.1
ProcVersionSignature: Ubuntu 2.6.32-27.49-generic-pae 2.6.32.26+drm33.12
Uname: Linux 2.6.32-27-generic-pae i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Wed Jan 12 21:03:54 2011
ProcEnviron:
 LANG=de_AT.UTF-8
 SHELL=/bin/bash
SourcePackage: thunderbird

[David Ayers (ayers)]

User-Agent: Mozilla/5.0 (X11; U; Linux i686; de; rv:1.9.2.13) Gecko/20101206 Ubuntu/10.04 (lucid) Firefox/3.6.13
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.13) Gecko/20101208 Thunderbird/3.1.7

Mails sent from Thunderbird which merely contain BCC entries generate a TO: header in the de_AT.UTF8 locale like:

To: Verborgene_Empfaenger: ;

This header is successfully parsed by:
Microsoft Outlook Express 6.00.2900.3664
for example Outlook version:
Microsoft Office Outlook, Build 11.0.5510
does not decode these mails correctly.

The the raw MIME format including all the headers are presented.
I'm not sure whether the To header must contain a valid address,

Evolution warns about an empty To: header invoking an Apparently-To: header on some systems revealing the BCC recipients. Maybe a warning with the suggestion to add the sender as the To: recipient would satisfy both cases.

Reproducible: Always

Steps to Reproduce:
1. compose a mail leaving the To: field empty but adding an Outlook Build 11.0.5510 (Haven't had any feedback from to many other Outlook versions)
2. send the mail
3. receive the mail in Outlook Build 11.0.5510
Actual Results:
The mail is sent without a warning. A localized recipient is generated:
To: Verborgene_Empfaenger: ;
Outlook renders the raw MIME message including the headers as the mail contents.

Expected Results:
A warning about missing To: field would be great with a suggestion to enter the sender a value which can simply be confirmed. If the header:
To: undisclosed recipients: ;
is legal, then that message shouldn't be localized.
Outlook should render the mail.

Not sure if this is a real bug on the side of Thunderbird or if Outlook is being buggy but it the end user impression is that Thunderbird is sending buggy mails.

[Ludovic-mozillamessaging (ludovic-mozillamessaging)]

Can you look how things look in your send folder ?

Are you using exchange to send (as the to hearder might be added by the smtp server).

So you want :
1) a warning when To: header is empty
2) something else ?

I'm not sure about 2.

I'm also not sure having an empty TO: field is illegal. According to http://tools.ietf.org/html/rfc2822#section-3.6 te To: field is even optional.

[David Ayers (ayers)]

A BCC mail in the sent folder contains the following entries: (email addresses redacted)

From - Tue Jan 18 11:01:26 2011
X-Mozilla-Status: 0001
X-Mozilla-Status2: 00800000
X-Mozilla-Keys:
BCC: David Ayers <email address hidden>
Message-ID: <email address hidden>
Date: Tue, 18 Jan 2011 11:01:22 +0100
From: Pezi Ayers <email address hidden>
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.13) Gecko/20101208 Thunderbird/3.1.7
MIME-Version: 1.0
To: Verborgene_Empfaenger:;
Subject: test
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
Content-Transfer-Encoding: 7bit

test

That same mail on the receiving side show only Postfix MTA's but the TO header is already there with the localized recipient place holder. Note that a mail sent via Evolution does /seem/ to omit the To header and someone else /seems/ to insert the To header:

Subject: test
From: David Ayers <email address hidden>
Content-Type: text/plain; charset="UTF-8"
Date: Tue, 18 Jan 2011 11:13:55 +0100
Message-ID: <1295345635.2446.42.camel@schiefer>
Mime-Version: 1.0
X-Mailer: Evolution 2.30.3
Content-Transfer-Encoding: 7bit
Bcc: David Ayers <email address hidden>
X-Evolution-Format: text/plain
X-Evolution-Account: 1225452871.12979.0@rosenquarz
X-Evolution-Transport:
 smtp://user%40domain.org;<email address hidden>/;use_ssl=when-possible
X-Evolution-Fcc: mbox:/home/ayers/.evolution/mail/local#Sent

which is received as (lots of redactions):
Return-Path: <email address hidden>
X-Original-To: <email address hidden>
Delivered-To: <email address hidden>
Received: from localhost (localhost.localdomain [127.0.0.1]) by
...
Subject: test
From: David Ayers <email address hidden>
Content-Type: text/plain; charset="UTF-8"
Date: Tue, 18 Jan 2011 11:13:55 +0100
Message-ID: <1295345635.2446.42.camel@schiefer>
Mime-Version: 1.0
X-Mailer: Evolution 2.30.3
Content-Transfer-Encoding: 7bit
To: undisclosed-recipients: ;

but this message leads to the same issue with the noted outlook version:
See: https://bugzilla.gnome.org/show_bug.cgi?id=639372

Thanks for looking in to this!

[David Ayers (ayers)]

My suggestion is to add a dialog when the user clicks send (validating the mail) that warns about an empty To: field that this may cause issues for some MTA and/or email clients. This dialog could also suggest adding the sender as the recipient of the To: field. The dialog could then have three buttons: Cancel, Send with sender as recipient, Send. Default being Send with sender as recipient.

[gf (gf-interlinks-deactivatedaccount)]

Hello David,
Thank you for submitting this bug and reporting a problem with BCC only emails in Thunderbird.

You made this bug report in 2011 and there have been several versions of Ubuntu and Thunderbird since then.

Could you confirm that this is no longer a problem and that we can close the ticket?
Or, if it is still a problem, could you run the following (only once):
apport-collect 702097

and upload the updated logs and and any other logs that are relevant for this particular issue.

Thank you again for helping make Ubuntu and Thunderbird better.

G

[Paul White (paulw2u)]

No reply to gf's request for information
Previously no comment here since 2011
Upstream bug has also seen no action since 2011
Ubuntu 10.04 (lucid) reached end-of-life on May 9, 2013
Marking "Invalid" to close and reduce backlog

[Vseerror (vseerror)]

I don't think we'd bother with such an obscure issue. But I could be wrong

[Bugzilla2007 (bugzilla2007)]

(In reply to Wayne Mery (:wsmwk) from comment #4)
> I don't think we'd bother with such an obscure issue. But I could be wrong

Yeah, [lacking any other reports](https://bugzilla.mozilla.org/buglist.cgi?quicksearch=%3Athun%2Cmailn%20undisclosed-recipients&list_id=16122726), this doesn't seem to be a big issue - but I'd feel better if we could test this against a recent version of Outlook before closing the bug.

Both `To: undisclosed-recipients: ;` or localized equivalents like `To: Verborgene_Empfaenger: ;` are valid syntax, `named groups` per [rfc5322](https://datatracker.ietf.org/doc/html/rfc5322#section-3.4), last updated Oct. 2008:

> group = display-name ":" [group-list] ";" [CFWS]

Thunderbird's usage is explicitly mentioned in the specs (see bold format added by me):

> When it is desirable to treat several mailboxes as a single unit (i.e., in a distribution list), the group construct can be used. The group construct allows the sender to indicate a named group of recipients. This is done by giving a display name for the group, followed by a colon, followed by a comma-separated list of any number of mailboxes (including zero and one), and ending with a semicolon. Because the list of mailboxes can be empty, **using the group construct is also a simple way to communicate to recipients that the message was sent to one or more named sets of recipients, without actually providing the individual mailbox address for any of those recipients.**

So Thunderbird isn't doing anything wrong technically, and as reported, this would be a bug in Outlook.

That said, imo it's quite easy for the user to send to a group of `BCC` recipients without adding a `To` recipient, iow it's quite easy to send out messages having `To: undisclosed-recipients: ;` syntax. *If* such messages are still breaking in Outlook (which I doubt), we should probably explore better options than letting plain vanilla messages break in Outlook without much benefit.