[lugm.org] duplication of topics

[Daniel Shaw]

As I posted before - the duplicates originate from the sender. That is, when there are duplicate posts, if you analyse the headers, there are in fact two separate posts sent to the list server from the person posting.

That initial observation was based on headers from a particular post from Ronny. However, as you probably noticed it occurs from other posters as well.

The basic root cause is described here:
https://mail.python.org/pipermail/mailman-users/2008-December/064285.html

I'll also expand on this below. If you read the link above though you can stop reading here if you choose. The rest of this repeats that in more detail.

It is not really a mis-configuration of the list. It can be interpreted as such, but more accurately it's a mix of the way the list is configured in two different area and also human beahviour.

In short: If you send email to either of discuss at discuss.lugm.org or [discuss at lugm.org](mailto:discuss at discuss.lugm.org) both work just fine and go to the list. That is, one or the other is an alias to the other one. I don't have access to the server, so cannot say which is the "real" list and which is the alias.

That is a reasonable setting, that is not uncommon, not only for lists. Many mail systems accept <localpart>@<domain.tld> as well as <localpart>@<hostname.domain.tld>

The in addition to that, mailman has a setting where you can choose how to set the reply-to header - either the list address or the original posters address. Both have pros and cons. For whatever reason, LUGM has chosen the later. That is, the reply-to header is set to the poster's personal address, and thus for mail clients that respect the reply-to header (almost all), if you click "reply" you reply only to the poster, and not to the list.

This is where human behvaiour comes in - most of us therefore click on "reply to all", which most clients support. The intent is to include the original poster directly and also post back to the list. However, in the case where the post was to the alias, the list server's mailer forwarded the original post to the actual list, but the original recipient address is also maintained in headers. So when someone does a "reply all", this then includes both valid list addresses. Seperately.

There are 4 possible solutions to this:

1. No list settings change, but people always double check the recipient list when doing a reply to all in a client, and edit out the duplicate mailing list addresses manually. yea right. people are never going to mess this up when replying in a hurry...? riiighhhtt...

2. The smtp on the list server is re-configured to re-write the list address in such a way as to also discard the alternate address completely. How to do this, and if it's even possibe depends on the MTA used, it's version and what other emails are done on the system if any.

3. Patch mailman with a custom handler written in 2008 as linked from the above archive link. If it still exists. If it still works on current mailman. Good luck maintaining that next time Mailman needs patching for other reasons...

4. Probably the simplest solution. Change the list config such that reply-to is set to the list address. Then, in the majority of cases, people will learn to do just "reply" and not "reply all". There'll still be some instances where reply to all is used and we get duplicates. But I think this'll be less frequent that we see now and likely to decrease over time.




-------- Original Message --------
Subject: Re: [lugm.org] duplication of topics
Time (UTC): October 9 2015 9:32 am
From: z.coldplayer at yahoo.co.uk
To: discuss at discuss.lugm.org




Why is my message sent once is on two different topics, ie 3rd 4th.
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