You notice that your Outlook Web Access shows your last received email is before midnight on New Years Eve December 31, 2021. Let's call this the Y2K22 Bug. According to numerous reports from Microsoft Exchange admins worldwide, a bug in the FIP-FS engine is blocking email delivery with on-premise servers starting at midnight. This is caused by Microsoft using a signed int32 variable to store the value of a date, which has a maximum value of 2,147,483,647. But, dates in 2022 have a minimum value of 2,201,010,001, which is greater than the maximum value that can be stored in the signed int32 variable, causing the scanning engine to fail and not release mail for delivery.

Check the Exchange Server's Event Log for an error or errors similar to this “The FIP-FS Scan Process failed initialization. Error: 0x8004005. Error Details: Unspecified Error” or “Error Code: 0x80004005. Error Description: Can't convert “2201010001” to long.”

How do you fix this? Here is a temporary fix until Microsoft issues Exchange updates addressing this problem. Either disable or bypass anti-malware scanning, and then restart the Exchange 2016 Transport Service, all using Exchange PowerShell.

I recommend to Bypass Filtering rather than disabling the anti-malware service.

See: [Disable or bypass anti-malware scanning[https://docs.microsoft.com/en-us/exchange/antispam-and-antimalware/antimalware-protection/antimalware-procedures?view=exchserver-2019]]