How to setup Reverse DNS on Mara?

[Greg Platt - Platt Consultants]

I'm hosting a dedicated server using Debian v3.0.r4 and running Mara as my
DNS server. The server presently hosts about 2 dozen domains.

Apache 2 runs in virtual host mode on my server which means the server has
only 2 IP addressees - not 2 per domain - just 2 for the entire server. For
many hosts today's email rules seem to require a valid Reverse DNS entry for
each domain on a server. But I did not know how to set up Reverse DNS when I
installed Mara and even now know very little about how this works (or should
work) in a virtual hosting environment..

However, it has become evident to me that I'm going to NEED to setup reverse
DNS because some servers now reject all inbound email if it they cannot find
a valid Reverse DNS pointer for the domain (or is it for the server?)
sending the email. Lately, I'm getting complaints from users about emails
they send bouncing back to them for mysterious reasons with cryptic error
messages.

I've concluded one reason for that is the lack of any reverse DNS pointers
in Mara. But I'm not sure how to set them up and the Mara docs are ominously
silent on this subject. Although they do at least mention they support PTR
records which I gather are part of what is required to create reverse DNS
entries.

Have I overlooked something here? Or can someone explain to me what needs to
be done to provide valid reverse DNS entries in Mara?

Thanks!