From email addresses sometimes strange on this list - was Re: [beginner] What's wrong?

[Cameron Simpson]

On 05Apr2016 08:58, Chris Angelico <rosuav at gmail.com> wrote:
>On Tue, Apr 5, 2016 at 8:55 AM, Michael Torrie <torriem at gmail.com> wrote:
>> Usenet-orginating posts look fine.  For example:
>>
>> From: Marko Rauhamaa <marko at pacujo.net>
>> Newsgroups: comp.lang.python
>>
>> Whereas email ones are sometimes looking like this:
>>
>> From: Mark Lawrence via Python-list <python-list at python.org>
>> Reply-To: Mark Lawrence <breamoreboy at yahoo.co.uk>
>
>Ohhhh.... That probably explains it. It's because of Yahoo and mailing
>lists. Yahoo did stuff that breaks stuff, so Mailman breaks stuff
>differently to make sure that only Yahoo people get messed up a bit.
>It means their names and addresses get slightly obscured, but delivery
>works.

It is yahoo and mailman and a funky spec called DKIM or DMARC (related, not 
identical).  This makes a signature related to the originating host, and if 
mailman forwarded the message unchanged the signature would break - people 
honouring it would decide the mailman hosts were forging Mark's email.

Fortunately you can fix all this up on receipt, which is why I wasn't noticing 
this myself (I had in the past, and wrote myself a recipe for repair - my mail 
folders contain the reapired messages).

For Mark's messages I am using these mailfiler rules (the latter I think):

  from:s/.*/$reply_to/
            X-Yahoo-Newman-Id:/.
            from:python-list at python.org,python-ideas at python.org,tutor at python.org

  from:s/.*/$reply_to/
            DKIM-Signature:/.
            from:python-list at python.org,python-ideas at python.org,tutor at python.org

which just replaces the contents of the From: line with the contents of the 
Reply-To: line for this kind of message via the python lists.

Yahoo do something equivalent but more agressive to lists hosted on yahoo 
itself, such as sed-users. For that I have a couple of scripts - fix-dkim-from:

  https://bitbucket.org/cameron_simpson/css/src/tip/bin/fix-dkim-from

which is a sed script, and fix-dkim-from-swap:

  https://bitbucket.org/cameron_simpson/css/src/tip/bin/fix-dkim-from-swap

The former works on messages whose From: header is enough - it can be reversed 
in place. The latter is for messages where the from isn't enough, but there is 
another header contianing the original (default "X-Original-From").

You can use these in systems like procmail, eg:

  :0whf
  * from:.*<sed-users at yahoogroups.com>
  | fix-dkim-from

It is annoying, and I'm happy to help people utilise these recipes if possible.  
Most all-in-one mail readers (Thunderbird, GMail, Apple Mail etc) are a bit too 
dumb, but if you can do your mail collection separately from your reader you 
can usually insert something in the processing.

It is nowhere near as annoying as the usenet<->mail gateway which is eating 
message-ids; that is truly uncivilised.

Cheers,
Cameron Simpson <cs at zip.com.au>