junk email folder not syncing on my phone

Hello, this is my issue. On a Lumia 920; with my primary MS account/email. A couple of days ago, I went through my email 'junk' folder and deleted over 300 junk emails, tapped sync. When I log into Outlook on a desktop, the Junk folder is up-to-date; as in, all the deleted junk-mails are gone. When I check the Junk folder on my phone, it still shows all the 'deleted' e-junk, plus anything recently arrived. I have tried tapping 'sync' in the email app, I've gone to 'settings-email accounts-long tap the account in question and tap 'sync'. I've tried these steps multiple times,with and without WiFi, before and after a soft re-boot. Note, this syncing does not put the junk mails back into my account, as they are not there when I log on through a computer, they only show on my phone.