It seems OnPremise Microsoft Exchange servers are having mails queued up due to an issue with a Virus and Malware scanning engine of Microsoft Exchange server. This bug has blocked email deliveries starting from Jan 1st, 2022. This bug specifically occurs in the FIP-FS engine as that particular component is failing to convert the dates in 2022 and causing the component to crash stalling the messages. When you are having this issue, you may get an error message like this one shown below
The FIP-FS "Microsoft" Scan Engine failed to load. PID: 23092, Error Code: 0x80004005. Error Description: Can't convert "2201010001" to long.
The main reason this is occuring is due to the failure of FIP-FS Scan engine to covert the Jan 1st, 2022 to a signed int as 2201010001 is longer than 2147483647. Though there are couple of stop gap solutions, Microsoft has also released a patch for the same on it’s Website.
This bug might affect exchange server queues and even if it’s fixed it may take long time to users to receive the stuck emails according to Microsoft.