While to the other users that have similar email account which have been previously setup / synchronize there are no issue accessing / fetching the email account and esp the Inbox.
Do we have any idea on how to prevent this from happening again?
Current solution that I am doing to fix this issue is to do Compact All Forced on the said domain.
You’ll probably want to try without the purge option first (as that will just scan and not try to correct any problems), and ensure you have a back-up before using the purge option.