I'm intolerant of AOL bounces and on the first one IMMEDIATELY delete the
userid.  Often the reason is either for a full mailbox or a change (or
removal) of handle.  In either case, there's nothing that I or AOL can do
about it.

BTW, the same is true for some of the other ISPs, but AOL comes to mind
first since they are by far the largest installed base.

/Pete