Our monitoring over the weekend detected a backlog of spooled emails. In order to clear the backlog, the Support Team have scaled down importing (Mailbox Reader and Import Services). Additional Processing Units (PU's) have been scaled up to help clear the backlog and the team are currently monitoring the progress. We anticipate that the backlog will take around a day or so to clear.
We understand the root cause of the problem; a misconfiguration of an LDAP setting caused PUs to timeout resulting in an initial backlog, we also identified mailboxes setup to Poll, which is not best practice for customers with a large number of mailboxes. We have shared the details with Titan Support.
Please note we have not scaled down the journaling of live emails.