.ZIP files compressed with WinZip 12.x "Best Compression" mode get Unscannable verdict from SMSMSE 5.x and 6.x


Article ID: 177675


Updated On:


Mail Security for Microsoft Exchange


WinZip 12.x has a 'Best Compression' mode. SMSMSE treats .ZIP archives created with this option as Unscannable.

You may observe one or more of the following:

    • Attachments quarantined and replaced with a text file stating "Symantec Mail Security replaced with this text message. The original file was unscannable and was quarantined."
    • The Windows Application Event Log showing events from Symantec Mail Security with a category of "Unscannable":

      Scan Engine Error.  CSAPI DEC result: 0x28. An unknown container was detected by Decomposer."



SMSMSE is not able to unpack Winzip 12 best compression files.


This issue is fixed in SMSMSE 6.5.5.


  • Do not use Winzip 12 best compression methods.  Create archives in WinZip 12.x with 'Legacy Compression zip 2.0' mode.