My own instincts also lean toward sending a test message. I note the
following, however:

> Suppose I set a header to:
>
>          Auto-Delete = Yes, Manual, Delay (0), Probe (0)
>
> Would this produce a list of addresses that are returning bounced
messages,
> without actually deleting the subscriptions?
>
> I would then return the Auto-Delate setting to what it is currently, in
> order not to undermine how the list runs normally.

I take it you are running with Auto-Delete= Full-Auto, since the other
possibilities should be reporting bounced addresses already. The good news
is that you shouldn't have to change the Delay: I get bouncing addresses
reported while they are being monitored (before the delay has run out).

I would think you could also use Renewal= with Probe, since everyone on the
list would show as inactive for long enough to be due for renewal if you use
a reasonable interval. You could do a temporary rewrite of the Probe
template to include information about the list's reactivation.

However, I'm not confident those probes would work. My own tests show that
an address I know is bouncing (because it's an old, abandoned one of mine
and I have retested it) doesn't show up on the bounce report even when it's
being probed. I asked for help with this a short time ago, and nobody has
offered any suggestions.

Hal Keen