duplicate suppression, sieve, loops, redirect and lost email

[Lawrence Greenfield]

   Date: Fri, 30 Aug 2002 10:11:26 -0400
   From: Ken Murchison <ken at oceana.com>
[...]
   It can't, but it _should_ be capable of detecting that the user is
   trying to redirect directly to themselves and make it a 'keep' instead. 
   The bottom line is that the user is using the wrong action to keep the
   message.

Just to annoy Ken, I think I'll disagree with him here.

I believe that (in an ideal world) Cyrus should tolerate a redirect
"myself at example.com" and treat it as a keep.

It turns out that this is much trickier than it first seems,
though. At CMU, our users have a primary address
("leg at andrew.cmu.edu") but can also have other address
("leg+cyrus at andrew.cmu.edu") or other addresses at different domains
("leg at cmu.edu") that point to the same Cyrus INBOX. (But it gets even
more complicated! "leg at cmu.edu" might point to my Cyrus INBOX---but it
might go somewhere else, too.)

Our Cyrus server runs at "cyrus.andrew.cmu.edu", though. It's fairly
easy for it to understand that "leg at cyrus.andrew.cmu.edu" is the same
address as "leg" receiving mail with lmtpd.

So the problem is: how can we concisely tell whether a given redirect
address is the same address as the user who is executing the Sieve
script?

I've scratched my head some and can't come up with any decent way.

Larry