I have an end user who is on Outlook 2016 with on-premise exchange and we here inbox only updates when I click "Update Folder" in send/receive ribbon.
I tried cleaining the local cache on the inbox folder and let it rebuild as I found one article saying that this was a known issue.
But the issue came back once it was fully synced again.
I am stuck and what tricks to use to help troubleshoot, I hate rebuilding profiles as they are big distruption to the users day while their mailbox is downloading.
Try running Outlook in Safe mode or recreating the profile. How big is the OST?
7GB's so I try to hold the profile restore as a last resort
I haven't tried safe mode I will try that real quick
Ah yes, forgot to mention disabling AV/scanning/backup software :)
For a proper sync of emails, one must verify the profile settings. Take a look on here to know: how to fix Outlook sync issue