[Mailman-Users] Getting duplicates when people CC list

Tony G 4ylyh9g02 at sneakemail.com
Mon May 1 02:49:09 CEST 2006

Mark Sapiro wrote:
> .. you said when you receive duplicates, the list was
> addressed twice in the post, once in To: and once in Cc:. Thus, I am
> suggesting that the list actually receives the post twice and sends
> it twice and that's why you get two copies.

I mis-spoke. It only occurs in that one list when someone CC's the list.  I
would understand if it were in both TO _and_ CC.  Since all lists and MUA's
are different, people don't know whether to Reply or Reply-All, so it's
50/50 whether the list address will be in the TO _or_ CC, but most people
know to not double up.

> There may be something here with digests too, but I don't think so.

I have not asked about digests but I don't think I'll find anything there

> The process of your not getting a dup when I address my reply to both
> you and the list IS a Mailman process. You only get the direct message
> from me because you have requested no dups, and Mailman sees your
> address in the To: of my post so it doesn't send to you.
> This is not the case on the other list where maybe the list receives
> the post twice.

Remember that I am not involved in the discussions where I get the dupes.
I understand the mailman code filters possible dupes when TO = a
subscription address.

I have confirmation from a single Outlook user that I get dupes when they
do not.  (I wish I had a larger sampling of responses over a longer period
of time but I'll take what I can get.)  This points to an MTA issue and not
list or MUA.  I am now checking in that area.  Again the problem is that I
only get dupes to this one address when the list is in the CC.  I can't
believe an MTA bug would be that specific so it might be some timing issue,
a hiccup during greylisting processing, etc.

> I don't think it's Mailman per se, but I can't be sure without knowing
> what is happening. I still think it could be actually two copies of
> the post reaching the list, but the fact that no one else on the list
> admits to receiving dups makes this seem unlikely. I would like to
> help you get to the bottom of this if I can.
> I think the next thing is to collect both copies of some duplicated
> posts with full headers and examine the Received: chains in each to
> try to determine where the duplication is occurring. If you need help
> with this, you can post headers from duplicated posts to this list or
> send them to me off list, and I will try to help.

Over the last month or two I have been going over the headers myself and
the headers on each copy of the mails are exactly the same: same Received
path and time stamps, and same Message-ID (!!).  The only pattern between
what generates dupes and what does not is that the list address is in the
CC of duped mails - but only on that list, not in this mailman-users list.

Please allow me a few days to pursue the MTA route and I'll post a note
here to let you know if I find anything.  Based on your comments and info
from the other list I'm fairly convinced that I shouldn't be wasting any
more of your collective time.  But I will let you know what I find out.

Thank you kindly for your dedicated interest.

More information about the Mailman-Users mailing list