email or routing problem?

[DirtDawg]

I have an exchange 5.5 server. We upgrade our bandwidth last week. With the upgrade we got new Global ipaddress range. On Friday night the new DNS was sent out. So our DNs should be fine. When I look nslookup I see that we also have 4 mail forwarding servers and our Exchange server. The problem is that the mail forwarding servers are not always delivering the emails to our exchange server and delivering the outside users with undeliverable email message. Is this a problem with the Exchange server settings or a problem with the mail forwarding servers? Like I said sometimes they delivery email and sometimes they do not?

Thanks in advance.

 

[FrankTrib]

I would look in the logs of the Exchange and forwarding (unix/sendmail?) servers. When the messages are NOT delivered, are they returned as undeliverable or just lost?

Frank