> In a nutshell, you can pretty much ignore anything in the Advisory Reports
> folder, since it will just contain messages about who's been probed and/or
> dropped automatically.  These messages are only really useful to you in
> case somebody writes wanting to know why they've been dropped from a list
> by the Listserv software.  You can then search through the old Advisory
> Report messages and find out what happened to them and when.

This isn't 100% true.  Addresses for non-subscribers can appear in the
Error Monitor Report (issued to tell you what Auto-Delete is doing).
Since they are not subscribers, they will never be automatically
deleted from the list.  You can tell when this situation is occurring
because the error count will exceed the threshold at which automatic
deletion should have occurred.

The usual reasons for bounce messages being issued for addresses that
aren't subscribers are (1) the ISP changed the email address after the
person subscribed and now the account has been deleted, (2) a
subscriber is automatically forwarding mail to an address that no
longer exists.  In the first case, you can usually handle it by looking
for similar email addresses in your subscriber list.  In the second
case, you are up the creek (almost).  You need the Received headers of
the bounced message to see where the subscriber address is, but
LISTSERV's Auto-Delete is dropping them.  You can turn off Auto-Delete
(so you get all the bounce messages) or turn on Probe.

By the way, we've been seeing more instances lately of probe messages
being bounced to the LISTSERV address instead of the special probe
Return-Path address.  This is presumably because the email system
receiving the probe sends its bounces to the From address instead of
the Return-Path (aka Envelope From or SMTP MAIL FROM) address.  Such
misdirected bounces go to the LISTSERV postmasters.  We forward the
ones we get to the appropriate list owner, but if your LISTSERV
postmaster does not do that, you (the list owner) will never see them.