Error on Exchange server

I keep getting the following error. What is my problem?:

Event Type: Warning
Event Source: smtpsvc
Event Category: None
Event ID: 2012
Date: 1/28/2005
Time: 12:01:53 PM
User: N/A
Computer: PUMA
Description:
SMTP could not connect to the DNS server ‘xx.xx.xx.xx’. The protocol used was ‘UDP’. It may be down or inaccessible.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Data:
0000: d5 04 00 00 ?…