The mailing list for listmasters using Sympa

[IKEDA Soji <address@concealed>]

Hi Tim,

On 2023/02/07 4:01, Silvers, Tim wrote:
> Hi. We have had a couple of recent reports where a recipient of an email 
> sent to a Sympa list appeared differently to at least one recipient than 
> it did to other recipients of the same mailing.
>
> For example, an email was sent to the mailing list address@concealed 
> <mailto:address@concealed> and that was in the “To:” header to all but one 
> recipient who saw their own name in the “To:” header field with the 
> address of the list (e.g., “Charlie Brown <address@concealed>") with the 
> “Reply-To:” or Return-Path also including the recipient’s name along 
> with the list name.
>
> Has anyone encountered this before? Is it Sympa or is it some issue 
> client-side?

We have at least the following case: A side effect of DMARC Protection 
by Sympa.

1.  Suppose a list has DMARC Protection (see below) enabled.

2.  When a sender posts a message to the list, it is possible that the 
"From:" field is rewritten, e.g.,

  To: address@concealed
  From: Charlie Brown <address@concealed>

is rewritten to

  To: address@concealed
  From: "Charlie Brown" (via dogs Mailing List) <address@concealed>
  Reply-To: Charlie Brown <address@concealed>

3.  On the recipients side, some email clients may automatically be able 
to populate the "From:" field of the received email into the address 
book. Thus, the address <address@concealed> may be recognized as the address 
of Charlie Brown.

4.  In addition, the email client can display the address of the 
received email as the name in the address book. --- So, with such email 
client, a message with the address <address@concealed> in the "To:" field 
will appear as a message sent to Charlie Brown.

5.  And that's not all. To send e-mail to Charlie Brown, when a user 
types his name in the e-mail client, the address that is picked up from 
the address book for completion can be <address@concealed>.  --- The user 
could end up posting a personal email to the mailing list.


That's why we should make ARC widely available and make temporary 
workarounds such as DMARC Protection unnecessary in the future.


About DMARC Protection:
  https://www.sympa.community/manual/customize/dmarc-protection.html

About DKIM and ARC:
  https://www.sympa.community/manual/customize/dkim-arc.html


Regards,
-- Soji

> Thanks,
>
> Tim

--
株式会社 コンバージョン
ITソリューション部 システムソリューション1グループ 池田荘児
e-mail address@concealed
https://www.conversion.co.jp/