If I understand your question well, you wish to access the same email box on the Linux sever from two or more Win98 machines. If so, I see there are several ways you can do this:
1)
If you configure your mail client as IMAP (instead of POP3), you can access the emails on server Redhat from any Win98 machine. I am not sure OE supports IMAP or not, but many email client including Outlook2000 support IMAP.
2),
You can install some program and Apache to enable web-based email - like jwebmail, nwebmail, etc.. So you can just use browser from any of your Win98 box to access or send on the Linux server. All emails will remain on the Linux server. Nothing gets downloaded to local machine. Yes, you'll need Apache running on Linux and login authentication is quite secure.
3),
You can create another account, say Acct2, and have Acct1 always forward a copy of emails to Acct2, so both of your Win98 machine gets a same copy of incoming email, but make sure always use Acct1 as reply address to ensure both machine get a same copy of incoming emails, because Acct1 don't get a copy of emails sent to Acct2. The disadvantage of this is that you don't see same the sent items on both Win98 machine.
4),
You can use a network shared directory to store email client OE or Outlook *.pst files and have the two Win98 machine points to the same mailbox or directory. But in this case, only one machine can access email at a given time, otherwise 2nd machine will get sharing vialation or file lock problem.
Out of the 4, which one you like most? I think there are some more ways to do it.