Stale DNS Records

[pantherguy]

We are having trouble with a local business emailing us. It started just after we changed our mail filtering service. Here is the bounce back message they get:

Your message could not be sent.
A transcript of the attempts to send the message follows.
The number of attempts made: 1
Addressed To: user@domain.com

Fri, 05 Sep 2008 15:00:02 -0500
Failed to send to identified host,
user@domain.com: 147.202.xx.xx (our old mail filtering ip, 553 sorry, mail relay to user@domain.com prohibited, please authenticate or set up relaying
for 69.66.xx.xx (there mail server ip) unknown (#5.7.1)
--- Message non-deliverable.

Why is there outbound mail pointing at our old mail filtering ip? We are having no other problems with anyone else. I talked to our ISP support and they said, "They could certainly have stale DNS entries on their end that would cause that, as I do show that IP is not any one of your current MX's." Does this sound like it could be the issue? What do I need to tell the company that's trying to send to us?

Thanks.

[johnwill]

I'd guess this is really a spammer that has latched onto your email address and is spoofing it to send his spam. This is pretty common, it normally dies out after a couple of weeks when they pick on someone else. I've had this happen twice to my domain over the years, nothing to do but weather the storm.