Find out why it changed and what needs to be corrected on your end to insure it will work. It may be only a delay in the cache being used by other servers.

A reverse lookup is done to insure that server1.anyother.xxx knows it's your server sending either email, web pages, or whatever. The PTR record is used to show that 10.140.50.1 is equal to your server server1.somewhere.gov when server1.somewhere.gov was shown to be from a certain IP.

If I try to send information to SUN from my internal servers via email, it won't accept it. That is because when SUN gets the email, it looks up the name of where it came from (let's say server1.intermedia.com) When SUN's email server does a reverse lookup, it finds out the DNS servers for intermedia.com, request the name of the IP for server1.intermedia.com. If that does not match what it reads from the info it received from my server off the email connection, then it refuses the email due to the possiblity that is was forged. Some sites just set the message as possibly being forged. Some sites reject it.

my nameserver record has changed on my DNS configurartion(I don't know why) from something.gov to somethingelse.gov. Same IP, though.

When a reverse lookup is performed on the other end to verify my identity. Is it looking for the entire name or is it just verifying my IP addx is a .gov address?