If you are receiving errors about being close to your quota for your Exchange e-mail account, you should consider archiving your older messages. Archiving copies old e-mail messages and attachments to an Archive.rge file (you can change the name during with the manual export process) and then removes the data from the Exchange mailbox decreasing its overall size. Items moved to an Archive.rge file are still accessible by opening the file through Entourage, and should be included in regular backups to prevent lost data. If you need more assistance in managing your mailbox size, see the Quota Management page.
Entourage allows users to delete items once they've been archived, however, any item that is on the server that is being archived will be deleted. You might want to choose the No option, then manually delete items after the archive. Make sure that you Purge Deleted Items, however, to fully free up the space from the archive. Click the right arrow to continue.