The mailing list for listmasters using Sympa

[Cefiar <address@concealed>]

On Thursday 08 May 2008 11:02:04 Adam Bernstein wrote:
> >  From my testing, I can see that if a message is sent to multiple Sympa
> > lists and a recipient is a member of more than one of these lists, only
> > one copy of the message is received.
>
> Nope, it doesn't have any way to de-duplicate deliveries like that.
> Subscriber to multiple lists receives a copy from each one.  Must be
> something else going on in your testing.

FWIW: Some mail storage systems do this deduplication automatically. One of 
the many ways to identify a duplicate is using the Message-ID: header.

If the list emails all go out with the same Message-ID header (which, given 
they're the same originating email, and the Message-ID header is preserved, 
should always be the case), then it's quite possible that this can happen. 
Same thing happens if your MTA decides to deliver to multiple "local" 
addresses (local to the mail storage system) at the same time.

I tripped over this issue with Cyrus, which does this by default (and caused 
a 
fair bit of CC'd mail to vanish inconsistently). At least in the case of 
Cyrus, this behaviour can be changed. If the system has some other type of 
storage engine (eg: a built in proprietary one), then you should check if 
there is an option somewhere for it. Hopefully you won't be out of luck.

PS: Another (slim) possibility is that each message got delivered separately, 
and that one has hit a slow MX somewhere along the line. I've had this with a 
number of ISP email accounts, where one of the MX's for their domain seems to 
hold on to mail for 12-24 hours for absolutely no conceivable reason before 
forwarding it on to another MX or to their storage back-end.

-- 
 Stuart Young - aka Cefiar - address@concealed