I just posted:

>When editing my log files I've noticed that some of the messages have a
>header line In-Reply-To:. Is this something that Listserv is, or will be
>using, when threading the archives? In other words, is there a reason for
>me to save this header line?

Apparently this isn't what I thought it was, a newsgroup type of reference
to the prior message. They are all the same! The example being:

In-Reply-To:  <[log in to unmask]>

Don.