DNS – Mailservice problems

As of May 13th I have not been able to send mail to a particular domain. Here are the specifics (at the bottom ther are two excerpts from the MailService log file)….
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Darwin <hostname>.com 6.8 Darwin Kernel Version 6.8: Wed Sep 10 15:20:55 PDT 2003; root:xnu/xnu-344.49.obj~2/RELEASE_PPC Power Macintosh powerpc

May 13 2005 12:12:25 SMTP connection attempt for host "marshpm.com" using DNS Cache values.
May 13 2005 12:12:25 DNS Cache for Host "marshpm.com" will expire at: Fri, May 13, 2005 12:52:35.
May 13 2005 12:12:25 SMTP connected to server "mail3.mcapp.com:25" using TCP/IP to send data for host "marshpm.com".
May 13 2005 12:12:25 SMTP Sent Message ID: 427864, Size (k): 19, Recipient(s): 1, Message transfer time: 00:01, Total delivery time
: 00:05.
May 13 2005 12:12:26 SMTP closed connection to TCP/IP server "mail3.mcapp.com".
May 13 2005 12:12:26 Total messages transferred: 1
May 13 2005 12:12:26 Total data transferred (k): 19
May 13 2005 12:12:26 Total recipients transferred: 1
May 13 2005 12:12:26 Total connect time: 00:01

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May 16 2005 09:05:21 SMTP connection attempt for host "marshpm.com". DNS Cache entry has expired. Retrieving new DNS cache entries.
May 16 2005 09:05:21 SMTP failed to connect to server "marshpm.com:25" using TCP/IP during connection attempt for "marshpm.com".

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The first entry in the log file shows that the marshpm.com domain will use mail3.mcapp.com as its mail exchanger. For this entry the email goes through.

The second entry shows the DNS Cache is expired and now it is not able to determine the correct MX and just uses the marshpm.com:25. This email does not go through.

It seems that the problem happened after the DNS cache expired. It also seems that perhaps it was unable to retrieve new DNS cache entries. Thus, it is using the host name instead of determining the correct MX record.

What do I need to do to get this fixed?

Thanks
Mark