possible dns issue

Hi fellow techies,

The problem: I can’t connect to SOME machines on my WAN sites.

The facts are:
1. The same users I can’t connect to can connect to machines at other sites (and get email)
2. I can connect to (and ping) the problem machines using thier IP address ONLY
3. There are ptr and name records for the same machines I can’t connect to in DNS.

I figured that if you can connect to a machine with a IP but not a name that the problem lies in the DNS. But I can’t seem to find a reason for the problem in my DNS.

Does anyone have any ideas how to fix this ?