1.8d doesn't process AOL bounces the same way it processes
standard-compliant bounces, but it uses passive probing to get the
same effect.

If you have passive probing enabled (which you do by default if you
have full auto-delete), then some fraction of addresses will be
passively "probed" each day (the fraction is determined by the value
of probe, which I think defaults to 30, which would mean that on
average, your whole subscribership will be probed every 30 days,
approx. 1/30 each day -- it's not exact because your list is
presumably changing constantly).

What happens is that when a message goes out to the list, some number
of people will be sent an individual message (instead of batched
together will all the other subscribers), and this message is
specially coded to uniquely identify the recipient. The message looks
perfectly normal as far as the recipient is concerned, and will not
look any different from any other message from the list. However, if
that message bounces, LISTSERV will know exactly which address
bounced, even though the bounce message may be non-standard. If it
does bounce, it will keep probing that address for the number of
days specified in your auto-delete delay setting.

So now, if passive probing is enabled (it can be disabled by setting
the probe value to 0), LISTSERV no longer sends bounces it can't
understand to the errors-to address. Instead it throws them away,
knowing that if the bounces are permanent, they will eventually be
taken care of by the passive probing.

This is why you never see AOL bounces anymore, but do see the
occasional AOLer getting auto-deleted.

Francoise