Using a blacklist to force compliance with some perception of normality
is a double edged sword. It may work, but if the blacklist is not cleaned
up in time it will collect innocent parties. Once enough innocent parties
have been collected people will stop using the blacklist.
Except I'm talking of local MTA blacklists which normally do not get
cleaned up except every few months or years. If you find your IP
unfairly blacklisted by local MTA admins then you have to contact the
admin of every MTA to get it removed from each.