What should I do when a password-protected ZIP file is not identified as a password-protected file?

For Google Workspace.

For Microsoft 365.


We have set up to except password-protected ZIP files from being zip-encrypted.
However, an email under the condition was not identified as a password-protected ZIP file.
Why does this occur?


When you encrypt a file on your PC and attach it to an email, that might be identified as a
non-password file due to compatibility issues with your OS or ZIP client in some cases.

【Known cases】

  • When you specify UTF-8 as an encode for your ZIP file name.
    *Please turn off UTF-8 encode function on your ZIP archive settings if applicable.
  • When you zip-encrypt an entire folder on your PC and attach it to an email.
    *If you have multiple files, do not put them into a folder and please archive them with multiple file selection.
  • When you zip-encrypt only 0 byte files.
    *Please archive files with at least a one byte file.
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