Address removed from CC-list

[Tom de Vries]

I've run into the following behavior of mailman:

I sent an email and CC-ed <email address hidden>, who also is a member of mailing
list <email address hidden>, which I also CC-ed:
...
CC: <email address hidden>, <email address hidden>
...

When looking at the copy I got from the mailing list (I'm also a member), the
email appeared as:
...
CC: <email address hidden>
...

I saw this and thought I forgot to explicitly CC <email address hidden>, and had to
go back to my sent box to find that I did indeed explicitly CC that address.

So mailman is losing information when forwarding the email, and in my view this
is a bug.

The behavior is coupled to the member.receive_list_copy property (Subscription
Option 'Avoid duplicate copies of messages?'), but I don't see why not sending a
copy should mean removal from the CC-line in other copies.

I suspect the behavior is due to the last 2 lines in this snippet from
src/mailman/handlers/avoid_duplicates.py:
...
                if send_duplicate:
                    msgdata.setdefault('add-dup-header', set()).add(r)
                    newrecips.add(r)
                elif r in cc_addresses:
                    del cc_addresses[r]
...

[Mark Sapiro (msapiro)]

Are you reporting this for Mailman 2.1 or 3.0? The handler you reference is the Mailman 3.0 handler, but I suspect your observation of the behavior was on a Mailman 2.1 list.

In any case, this behavior is intentional by design. Cc: recipients who are list members with their 'avoid duplicates' option set are removed from the Cc: list to keep that list from growing excessively in long threads with many 'reply-all' replies.

[Tom de Vries (tjvries)]

Mark,

thanks for looking into this.

I now also found some relevant prior discussions:
http://mail.python.org/pipermail/mailman-users/2006-May/051192.html
http://mail.python.org/pipermail/mailman-developers/2006-May/018777.html
http://osdir.com/ml/mailman-users/2013-05/msg00090.html
https://bugs.launchpad.net/mailman/+bug/266161

> Are you reporting this for Mailman 2.1 or 3.0? The handler you reference is the Mailman 3.0 handler, but I suspect your
> observation of the behavior was on a Mailman 2.1 list.

Yes, version 2.1.13. Is the 3.0 behaviour different?

> In any case, this behavior is intentional by design.

Perhaps it would be good to document this, f.i. here ( http://www.list.org/mailman-member/node21.html ) like this:
...
If your address appears there, then Mailman can be told not to deliver another copy to you. A side effect of this is that your email address will be stripped from the CC-list in the copy to others, to keep that list from growing excessively in long threads with many 'reply-all' replies. This has the consequence that others will not able to tell from their copy whether you were explicitly CC-ed or not, and a reply-all from others to the list copy will not explicitly cc you.
...

> Cc: recipients who are list members with their 'avoid duplicates'
> option set are removed from the Cc: list to keep that list from growing excessively in long threads with many
> 'reply-all' replies.

For me, the size of CC-list is not a problem, dropping CC-list members is a problem.

Of course there are others that would like other behaviour, f.i. this bug report here https://bugs.launchpad.net/mailman/+bug/266682

Perhaps we can add a configuration option prune_adressee_lists=lists/who with settings:
- none/none (my preference)
- cc/avoid_duplicate (current behaviour)
- cc+to/all (266682)