Hi,
Please first check the Sync Issues folder to see if there is any related error logged. To get to the Sync Issues folder, press Ctrl + 6 to switch to Folders module, find the folder form the left pane.
If we select Deleted Items folder and then click the Update Folder button under Send/Receive tab, will the Deleted Items folder get synced?
We can also try right-clicking on Deleted Items folder, selecting Properties, and then clicking the Clear Offline Items button. This will clear all items in the Deleted Items folder. Then, go to Send/Receive tab, click the Update Folder button to sync all deleted item back. After that, test if the Deleted Items folder syncs with the mail server.
Please let me know the result.
Regards,
Steve Fan
TechNet Community Support