[Mailman-Users] Problem with Archives and Threading

[Dan Mick]

> Ok, its Monday so maybe I'm missing something. I've tried to find the answer 
to my problem on Google and this list's searchable archives, but I failed to 
find one so here goes.
> 
> I'm using Mailman 2.0.13 on Redhat 7.2, with Apache 2.0.40, Python 2.2.1, and 
Sendmail 8.11.6. Install was successful and without incident. Overall operation 
is running smoothly. Message archives are viewable but are not threaded. They 
all show as a new message.
> 
> Now, in my searching I came across something about a "In-Reply-To:" field/line 
in the message header. I noticed that was non-existent in my replied, would-be 
threaded, messages. I am testing with a Hotmail, a Yahoo, and a Novell Groupwise 
account. None of which seem to create this required "In-Reply-To:" line.
> 
> Is the In-Reply-To: line requred? Is this a function of the email client, or 
MTA?
> 
> Ein B. :-)

Never been 100% clear on this either, but:  

1) looks like the code uses In-Reply-To: or References:
2) yes, it has to be the email client that adds the header, and not
   all do
3) mine often don't work right either and I've never spent the time to
   figure out just what's wrong (if it's just a bunch of email clients
   that do it wrong or not at all, or if there's a bug).