Hey, the reverse ip is really going to affect your mail. You can find more info on rdns at wikipedia. When you go to your domain it resolves to an ip. rdns is just a means of matching the ip to a domain.
Code:
~ >#check the ip associated with thebestpaysites.com
~ > dig thebestpaysites.com +short
94.23.78.68
~># Now check the domain that is associated with that ip!
~>dig -x 94.23.78.68 +short
94-23-78-68.ovh.net.
You should be able to do this through ovh. Simply look for the rdns or 'reverse ip' manager. Find the corresponding ip, and set its rdns record to be thebestpaysites.com
You can also most certainly have multiple websites on the same server. You will simply need to configure the apache virtualhosts (or nginx, tomcat, etc. ) to route the corresponding domains to the correct document root.