We have added the ability for our customers to edit their Reverse DNS in our DNS Editor Member Tool:
https://members.sonic.net/websites/nameservers/host_records
This tool works for anyone with IP Address services with us; be it Colocation, Leased Server, DSL, or anything else with an IP address tied to it; you can now use this tool to assign the corresponding DNS records to those addresses.
This feature is most useful to those running their own mail servers and can also be of use to those people who want both the forward and reverse of their domain name to match.