question regarding recommended PTR record configuration with multiple mail sites hosted on same IP

[Albert Croft]

I appologise if I waste anyone's time-I just wish to be clear on something.

I often see mentioned that there should be a PTR record set up for a 
mail server, but what is the recommendation in a case where multiple 
sites share a mail server? In other words, there exists something like 
(I can provide actual hostnames/IPs, if needed):

host.domain00.com. IN A 1.2.3.4
mail.domain01.com. IN A 1.2.3.4
mail.domain02.com. IN A 1.2.3.4
mail.domain03.com. IN A 1.2.3.4

Should there be a PTR record for each name entry? Or just one, and if 
so, what should it refer to? I seem to recall seeing mention in an older 
copy of _DNS_and_Bind_ of some systems not behaving properly when seeing 
multiple PTR records-is this still the norm?

Thank you in advance for your time and consideration.

-- 
-Albert Croft