Help Needed: My RHEL5 box suddenly stopped accepting e-mails

[Mun]

Hi,

Particulars:
   Red Hat Enterprise Linux Client release 5.6 (Tikanga)

This last Thu morning (05.05.2011) my RHEL5 suddenly stopped accepting
e-mails from other than itself.  I don't know if the following is
related, but the following updates were done around the time of the
problem starting:

------------------------------ Delimiter BEGIN --------------------------------
May 05 08:28:43 Updated: xmlsec1-1.2.9-8.1.2.x86_64
May 05 08:28:44 Updated: 1:autofs-5.0.1-0.rc2.143.el5_6.2.x86_64
May 05 08:28:45 Updated: xmlsec1-1.2.9-8.1.2.i386
May 05 08:28:46 Updated: xmlsec1-devel-1.2.9-8.1.2.i386
May 05 08:28:46 Updated: xmlsec1-devel-1.2.9-8.1.2.x86_64
------------------------------- Delimiter END ---------------------------------

I have since downgraded those packages, but it hasn't helped.  My IT
department has checked various things and they say everything looks
okay--but there is no explanation for why my system won't accept e-mail.

I can watch the network traffic via tcpdump and send myself an e-mail
from our exchange server and I see my system and the exchange server
exchanging packets; but my system apparently is not accepting the
e-mail.  And exchange will eventually send a "Delivery Delayed" message.

If I can't get this resolved I will be forced to use Outlook :(

Any assistance would be *greatly* appreciated.

Regards,

-- 
Mun