[Mailman-Developers] Re: Please stop the cross posting

[Christian Tismer]

(Ken)
> Offhand, there seem to me to be two key items here:
> 
>  - mailman can unequivocally identify the message id and the recipients of
>    members of any lists which it is serving on the same host, so given a
>    decent architecture (modularized message flow tracking db) it should be
>    easy to provide users the option to inhibit receiving more than the
>    first copy of a cross posted message

Well, I forgot about that. This makes it of course easy.

> Um, it doesn't make sense to go external when all the info is available
> internally to mailman as a whole!  Instead, the internal infrastructure
> needs to be developed - something that should go on the list for modular
> mailman, or whatever it'll be...

Of course! For me, identifying the message was the problem,
but I should have known better.
And instead of waiting for a new Mailman generation, I see that 
this problem has two sides:
A message appears to have always an ID which is generated by
the email program (not sure if that is guaranteed, but very likely).
That means one could set up the sendmail (qmail, whatever) 
configuration in a way that it checks the incoming mail for 
duplicate IDs. This would also work for cross-postings to different
Mailman sites.
Having both would be perfect and would save bandwidth, but one
suffices to yield the desired effect.
Should I try to write a little filter which keeps track of message
IDs for a short period, and drops those already seen? This
would be a small Python tool for the email client side, not 
touching Mailman at all.

Looks quite practical to me. ciao - chris

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