ITEMA has updated the servers and emails are now flowing again. However, we will restart the servers at 18:00.

UPDATE (1/1/22 @10:45pm PST): We've created a solution to address the problem of messages stuck in transport queues on Exchange Server 2016 and Exchange Server 2019 because of a latent date issue in a signature file used by the malware scanning engine within Exchange Server. When the issue occurs, you'll see errors in the Application event log on the Exchange Server, specifically event 5300 and 1106 (FIPFS), as illustrated below:

You can read the full article here: Email Stuck in Transport Queues - Microsoft Tech Community