The reverse DNS is generally setup by the ISP who provides your static block of IP addresses. You should contact them and request the proper rDNS mapping of the FQDN of the host which handles the SmarterMail traffic to the IP address you want the rDNS for as they are, generally, the only ones with the access and capability to modify the IN-ARPA database for their address block allocation.
Bruce Barnes
ChicagoNetTech Inc
brucecnt@comcast.net
Phonr: (773) 491-9019
Phone: (224) 444-0169
E-Mail and DNS Security Specialist
Network Security Specialist
Customer Service Portal: https://portal.chicagonettech.com
Website: https://www.ChicagoNetTech.com
Security Blog: http://networkbastion.blogspot.com/
Web and E-Mail Hosting, E-Mail Security and Consulting