Here is my problem:

One user sends an email to the recipient, but they never get the
message.  The setup is they use an ISP for smtp and pop3 connection
and Microsoft SBS 2003 Exchange for storing the email.  Signed onto
the ISP web mail and was able to send this person an email which they
got.  Any message sent by Outlook reports that the message has been
sent and places the email in the sent items folder but the recipient
never get the message.  There has never been any error messages
regarding this issue.  I have stopped and uninstalled the virus
program from the machine but was still not able to send the person a
message.

I setup outlook on another machine using the same account information
and had the same issue.  If this recipient sends them an email, they
get it.  If he replies to that email the recipient get it.  It does
not happen to all email that is sent but to only a handful.  Any clues
and any help appreciated.