Interpreting a DNS report

[Tom Gill]

I am with a small ISP in Orlando, Florida.  Some of our users are
having problems sending email to others and are receiving returned
messages that say our email server has no reverse lookup.

When I go to www.dnsstuff.com and use the reverse lookup utility on
our mail server's IP (216.54.161.51), it comes back just fine
(sun-msg-1.orlandotelco.net).

However, when I go to www.dnsreport.com and do a reverse on the
161.54.216.in-addr.arpa zone, I fail some of the tests:

It says we have lame nameservers, and missing (stealth) nameservers. 
Can anyone help interpret these in English?  The results of the
dnsreport can be found here:

http://www.dnsreport.com/tools/dnsreport.ch?domain=161.54.216.in-addr.arpa

Thanks for your time,
Tom