The Attachment is true file type criteria allows you to create rules that take actions on messages based on the true file type of attachments a message contains.
Where the Attachment is file name or extension criteria makes decisions based on just file names and/or extensions, the Attachment is true file type criteria scans the headers of the files themselves for the identifying signatures.


  1. On the Scanning Criteria tab, click Advanced.
  2. Select the Attachment is true file type criteria.
  3. Click the true file type link.
    The Attachment True File Type screen appears.
  4. From the drop-down list, select Selected true file types or Not selected true file types.
  5. Select the true file types for Trend Micro Email Security to match on.
    • For Microsoft Office files of version 2007 or later, Trend Micro Email Security supports attachment true file type detection only when the files are not encrypted.
    • The Compressed file type of other includes only the following file types: ar, arc, amg, lzw, cab, lha, pklite, diet, lzh, and lz.