Problems sending and receiving email

I usually get 15-20 emails a day in my inbox, and recently that number has
dropped to 0-2. My boss who was cc'd on an email that was sent to me
forwarded it back to me and I received it. I have no idea how many messages I
am not receiving. Also, more recently I am not able to send emails to
addresses that I previously was able to. Even hitting reply doesn't work. I
get return messages sent back to me like the following:

A message (from ) was received at 18 Oct 2005
16:59:16 +0000.

The following addresses had delivery problems:

Removed for privacy
Permanent Failu Other address status
Delivery last attempted at Tue, 18 Oct 2005 17:01:15 -0000


-OR-


This is the Spam Firewall at ms4.tcnoc.com.

I'm sorry to inform you that the message below could not be delivered. When
delivery was attempted, the following error was returned.


Removed for privacy: host
164.116.126.2[164.116.126.2] said: 501 Unknown command (in reply to DATA
command)


Please help me! I run my business through my email, and I don't know what
I'm missing by not receiving emails! I have Outlook 2002.