Upgrade the server and client to version 8 or above and you can have thread emails…. this will show the whole conversation for each mail…..
Mail threads are easier to manage in Lotus Notes 7.0. For example, you can view them from the Mail Threads view. You can also display them while reading mail in the bottom pane through a new option in the Mail Preferences dialog box. Mail Preferences can also be set via policies, allowing administrators to distribute the same set of preferences to all users. These preferences may be locked down by the administrator, so end users cannot modify them.
You can also sort by subject in your Inbox and other mail views. And mail archiving has been enhanced. In addition, you can now display a view-level icon within your Inbox that shows whether you are the only recipient or one of several listed in the To and/or CC fields.