Microsoft Exchange on-premise server cannot deliver email starting on January 1st, 2022, due to a bug in the FIP-FS anti-malware scanning engine. Microsoft enabled the FIP-FS anti-spam and anti-malware scanning engine to protect users from malicious email. A bug in the FIP-FS engine is blocking email delivery on January 1st, 2022, according to numerous reports from Microsoft Exchange admins worldwide.
Microsoft uses a signed int32 variable to store the value of a date, which has a maximum value of 2,147,483,647, according to security researcher and Exchange admin Joseph Roosen. The maximum value that can be stored in the signed int32 variable is not enough to cause the scanning engine to fail and not release mail for delivery. The Exchange server's event log will show an 1106 error when this bug is triggered. The error is 0x8004005. "Error Code: 0x80004005" is the error details. Can't convert "2201010001" to long. Microsoft will need to release an Exchange server update that uses a larger variable to fix the bug.
The admins have found a way to enable the FIP-FS scanning engine to allow email to start delivering again. With this unofficial fix, delivered mail will no longer be scanned by Microsoft's scanning engine, which will lead to more malicious emails and spam getting through to users.
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