What to do with subscribers who bounce is a matter of list-owner
experience and patience.

To find those subscribers who are currently not receiving email:

Q listname WITH NOMAIL FOR *@*

Of course some subscribers might be on vacation and/or read the postings
through the WEB interface (if available) and not because you have
suspended them.

What *we* like to do (on a particular listname) when we do suspend them is

SET listname NOMAIL NOPOST FOR bouncer@host

This methodology assumes that we do NOT usually set a normal subscriber
to MAIL NOPOST.  Thus, this combination of NOMAIL NOPOST tells *me* that
we have suspended the user.  Thus a

Q listname WITH NOMAIL NOPOST FOR *@*

output IS indicative that  one of the list-owners saw fit to suspend the
subscriber who is NOT on vacation/WEB-only user.

One of the pleasant side-effects is that the subscriber can not then send
a nastygram to listname complaining about why they aren't receiving mail
(or otherwise send a "test" message).

YMMV.
/Pete