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.
The Attachment True File Type screen appears.
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.