By removing the Junk folder from syncing your PC back to the email server, you can reduce the amount of time Outlook spends syncing with the server. You will still receive emails going to this Junk email box but it will no longer "sync" back with the server. To do this:
- In newer versions of Outlook, go to the Folder tab a the top of the window
- Click on IMAP Folders in the IMAP section
- A window will pop-up, click [Query] to see a list of folder being synced via IMAP
- Scroll down to the list until you get to a folder called "Inbox.Junk"
- Select this folder and click [Unsubscribe].
- Click [OK] to save and exit.