Take a look at this...

Reverse DNS entries for MX records
ERROR: One of more of your mail server(s) have no reverse DNS (PTR) entries. RFC1912 2.1 says you should have a reverse DNS for all your mail servers. It is strongly urged that you have them, as many mailservers will not accept mail from mailservers with no reverse DNS entry.

Check out this DNS service at http://www.dnsreport.com/

Shouldnt all reseller & hosting businesses configure this properly?

What do you guys think?