Question : Can a new reverse DNS record break a MX record

I host my own mail server, use AT&T as an ISP. All my outbound mail goes out into the cloud from my server through a firewall using NAT and is seen by the outside world as originating from 216.60.7.226. I have no PTR record for 216.60.7.226. All inbound mail is routed to a totally different company called Aristotle.net that filters it for spam and viruses and forwards it to me, my MX record for the domain hotsprings.org points to aristotle.net.

I am not able to send ANY mail to anyone in the comcast.net domain, I receive a 4.4.7 error. I suspect it is caused by the lack of a reverse DNS pointer record. I am not blacklisted on any spamdatabase per the lookup in DNSstuff.com.

Two questions:
1. If I get my ISP to add a reverse DNS pointer record is there any chance that it will break my MX record??
2. Who should add this PTR record?

Answer : Can a new reverse DNS record break a MX record

1. The PTR record won't break your MX record. Email servers sending to you would usually not do a reverse DNS lookup first.

2. The ISP hosting your DNS should add the PTR record. Have it match your email server to the right IP. Example would be mail.xxx.com to 1.2.3.4 and test it to make sure it works. Reverse DNS is a prime way of checking for spammers by most ISPs.