Well, to summarize the returns so far:
 
It looks like the general word is "don't reissue userids".  That's nice,
and we already do it.  The fun part is that this week I'm killing off
1,957 old userids, and probably will be issuing around 1,000 or so new
ones.  This out of a total 3,300 or so userids.  In other words, 2/3 of
the accounts roll over each semester.  Unfortunatly, we (due to internal
concerns) end up forced into it in some cases.  So it's not a good general
purpose solution.  It does 95% of it, but the other 5% is still 5-10
garbage mail files a day right now...
 
I like the idea of asking "Where do I have users on Listserv lists?" and
taking appropriate (manual) action.  I have a LISTSERV at which I am a
postmaster.  I wish I had a solution for all the sites that don't have a
local LISTSERV that trusts them - the validation problem is sticky.  Any
ideas?
 
For those who run DIRMAINT or other packages that expire passwords - I
have a one-line mode that allows the SPOOL command to go to a NOLOG
userid.  It's versioned for SP/4 at any level, but it should work on
SP/3 if you find the equivalent part of the code.  We just let the
password expire.  This also makes it easier to deal with LISTSERV list
userids - just NOLOG them and there's no need to change the passwords
all the time (that's why I made the mod).  For those wondering how I
deal with the spool files piling up - our site policy is to summarily
purge any user reader file over 2 weeks old.
 
 
                                   Valdis Kletnieks