There are a few ways you can do this.
Novell created a plug-in for Outlook that will allow you to use the Outlook client with a GroupWise mail store. You do loose the functionality of Busy Search and Reoccuring Appointments. Everything else works pretty good. I have not used this with GW6, but if a 5.5 client will work with 6.0, then I am sure the Outlook plug-ing will also.
You can also use the client as a POP3 client. Just load POP3 services with your GWIA. I would create a second GWIA in your mail system since most DNS Blacklists test for a gateway running both POP3 and SMTP and label them to be open relays. Haveing POP3 on a different server will avoid this. The POP3 server will need to have access to the POA. Users will send mail through the SMTP gateway, so you will need to allow relaying for internal systems only. Users who go this route and want remote access will need to use WebAccess so you don't have to compromize security to acomodate them. This route also makes your users loose all functionality of a groupware mail system, only e-mail will work for them.
You also have IMAP4 and LDAP for email clients to use.
