This is not a fault with either Outlook or with GMS. This is included as part of the design of the IMAP protocol. The IMAP standard states that upon deleting a message, a flag should be updated to show the message as "deleted". It is up to the individual mail client as to how they convey this "deletion" to the end user. Most IMAP e-mail client tend to strike a line through each message that the user deletes.
Outlook does offer a setting to hide messages marked for deletion. In Outlook 2003 this can be found under – View > Arrange By > Current View – Hide Messages Marked For Deletion.
Although Outlook should continue to intermittently purge messages marked for deletion, typically when switching folders or when it is next restarted, you can force a purge by selecting the "Purge" option under the "Edit" menu.
Another way to bypass this inconvenience is to use Gordano’s Outlook plug-in – GMS Collaboration. In addition to providing rich, collaborative functionality for GMS users via Outlook, the client will automatically hide messages marked for deletion requiring no further user intervention.
More information about GMS Collaboration can be found here..
Keywords:outlook purge expunge delete collab