On Mon, 2005-01-17 at 17:17 -0800, william(at)elan.net wrote:
To answer your question in the way email is currently use you can not
be certain because:
1. Sender headers could be added by mail list for Resent- message
and you would not be able to tell which one was first
That's what I said.
2. Headers sometimes get rearranged, even Resent-* headers
Do they really? I have never seen this.
Then with all due respect, you aren't looking hard enough. Lots of software -
including the software I work on, which is widely deployed - routinely is set
up to rearrange headers in various ways.
Header rearrangement is in fact a requirement in some cases given that there's
a bunch of widely deployed software that *depends* on headers being in certain
specific orders.
Requests from our customers for information about how to configure specific
header ordering have gone down in recent years, but we still get them from time
to time.
Under what circumstances do
Resent-* headers get changed such that they'd change the answer we get
for the 'most recent sender', at an intermediate site? To what extent to
we need to care?
This is a very different question, and one which I don't know the answer to.
Certain forms of header reordering are pretty common, e.g. ones that move the
various content- fields to the bottom and place them in a specific order. Other
sorts, and in particular ones that would actually perturb the order of multiple
occurrances of a single field, are, AFAIK, nonexistant. However, I always try
to keep in mind that my own knowledge of what goes on out there is necessarily
imperfect.
Ned