Sorry to pop in, just happened to notice this thread. The groupwise administrator can set mailbox limits - I'm not one here so I'm not sure how to change or eliminate them. Below is from the groupwise help file

Dan

About Mailbox Storage Size Information

Use Mailbox Storage Size Information to view your mailbox size and to manage items to regain space. Your GroupWise® administrator may set a size limit on your mailbox. If your mailbox size exceeds the limit, you cannot send new items until you archive or delete some of your existing items.

If your mailbox size exceeds the limit, the Mailbox Storage Size Information dialog box automatically displays. You can also display this dialog box by clicking Tools > Mailbox Size or by clicking the Mailbox Size message on the status bar at the bottom of the GroupWise Main Window.

Use the View buttons to view items in the selected folder in descending order, from the largest file size to the smallest. You can stop the processing at any time by clicking Stop Query. Use the Archive and Delete buttons to reduce your mailbox size.