They must be mapped to Gmail's 'Sent Mail' folder. The same goes for Outlook's 'Sent Items'. Check the folder mappings in Outlook and make sure that Outlook's 'Deleted Items' is mapped to Gmail's 'Trash' folder.
(Gmail status would indicate: ‘Initial download in progress’). You can start sending and receiving emails from Microsoft Outlook right away, however we do not recommend changing your folder structure until the initial sync is completed.