Combining access lists with rDNS checks

I've been gradually developing two sets of access tables.
The first is used in smtpd_client_restrictions,
so it protects postmaster as well as the rest.
It's for places that send a lot of spam that I never
excpect to get any legitimate email from ever.
Mostly cable modems and dynamic-address DSL lines.

The second is larger and protects everybody except
postmaster. More residential lines, plus much of
Asia and Eastern Europe. I also use the unknown host
tests in smtpd_recipient_restrictions.

Now I want to start an in-between layer.
Address ranges where postmaster will accept a message
only if the source has valid rDNS.
What's the right way to do that? Can I use
reject_unknown_reverse_client_hostname on the right
hand side of an access table?


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