Outlook express and Linux email server

Hi,

I want to know if other people have the same situation as we have with
outlook express and linux email server (rh7.3) as described below:

Our email server is RH7.3 sendmail-8.11.6-27.73.  Suppose a user has 2
computers (say one at office, and one at home), and he sets up outlook
express to handle his emails on both computers and select "Leave a copy
of messages on server; Remove from server when deleted from 'Deleted
Items' ".  

Suppose he receives 10 new emails.  He goes to computer 1 and uses
outlook express to read these mails. They apprear as new mails (bold in
outlook express).  After he reads all of them, they appear as read mails
(not bold).  Then, he closes outlook express, and goes to computer 2.  He 
opens outlook express there, and gets these 10 emails.  The "problem" is
even he already read these emails on computer 1, they still appear as new 
emails on computer 2's outlook express.  

Another case is that if a user uses pine to read mails first.  The mails
will appear as read (no mark 'N') in pine.  However, when he opens
outlook express later, he still receive these mails as new (bold).  I
feel that the cause of this "problem" or "feature" is the same as above.

This "feature" bothers our users and I want to know if this is normal,
standard feature, or it is due to incorrect setting?  Is there any way to 
"fix" it?

Thanks for any help!

Hongwei