My mail is bouncing back from some clients with the following (identifying information struck out):
mxi5p.efgh.org[xxx.xxx.xxx.xxx] said: 554 5.7.1
<unknown[xxx.xxx.xxx.58]>: Client host rejected:
xabd-4 (in reply to RCPT TO command)
The problem is that my server's IP address is not xxx.xxx.xxx.58.
My hosts file reflects this, and both forward and reverse DNS checks show the correct IP, and hostname.
The server used to be at .58, but was moved a while back.
I haven't been able to find any way to correct this, and it is a major pain in the butt.