Applies to: Exchange Server 2013

Topic Last Modified: 2013-02-14

Transport rules offer you an array of capabilities to define and enforce your messaging security requirements. Transport rules are enforced by the transport agent, which can examine a wide range of file types as attachments to messages when the messages are scanned. The supported file types are listed here. You can establish a data loss prevention (DLP) solution that can include numerous rules, which allow you to take advantage of the existing Transport rules framework. In this way, DLP policies and Transport rules are linked, and it’s useful to know the file types that can be scanned by the transport agent as you develop a DLP strategy.

For more information about Transport rules, see Transport Rules. For more information about DLP policies, see Data Loss Prevention.

Note:
A DLP policy that includes sensitive information-related rules doesn’t serve the same function as attachment filtering, which is a method of controlling the attachments that users receive.
Tip:
DLP is a premium feature that requires an Enterprise Client Access License (CAL).

Transport rule predicates that scan attachments

The following Transport rule predicates scan the contents of attachments in messages:

  • AttachmentContainsWords

  • AttachmentMatchesPatterns

Transport rules can scan only the content of supported file types. If the Transport rules agent encounters an attachment that isn't in the list of supported file types, the AttachmentIsUnsupported predicate is triggered. The supported file types are listed in the following section. Any file not listed will trigger the AttachmentIsUnsupported predicate.

Compressed archive files

If the message contains a compressed archive file such as a ZIP or CAB file, the Transport rules agent will inspect the files contained within that attachment. Such messages are processed in a manner similar to messages that have multiple attachments.

Note:
The properties of compressed archive files aren’t scanned. For example, if the container file type supports comments, that field isn’t scanned.

Supported file types for Transport rule scanning

The following table lists the file types supported by Transport rules.

Category File extension Note

Office 2013, Office 2010, and Office 2007

DOCM, DOCX, PPTM, PPTX, PUB, ONE, XLSB, XLSM, XLSX

Microsoft OneNote and Microsoft Publisher files aren’t supported by default. You can enable support for these file types using IFilter integration. For more information, see Register Filter Pack IFilters with Exchange 2013.

The contents of any embedded parts contained within these file types are also scanned. However, any objects that aren’t embedded, for example linked documents, aren’t scanned.

Office 2003

DOC, PPT, XLS

None

Additional Office Files

RTF, VDW, VSD, VSS, VST

None

Adobe PDF

PDF

None

HTML

HTML

None

XML

XML, ODP, ODS, ODT

None

Text

TXT, ASM, BAT, C, CMD, CPP, CXX, DEF, DIC, H, HPP, HXX, IBQ, IDL, INC, INF, INI, INX, JS, LOG, M3U, PL, RC, REG, TXT, VBS, WTX

None

OpenDocument

ODP, ODS, ODT

No parts of ODF files are processed. For example, if the ODF file contains an embedded document, the contents of that embedded document aren’t scanned.

AutoCAD Drawing

DXF

AutoCAD 2013 files aren’t supported.

Image

JPG, TIFF

None

Extending the number of supported file types

The supported file types listed in this topic can be revised at any time using IFilter integration. For more information, see Register Filter Pack IFilters with Exchange 2013.

The file types you add using this process become supported file types and no longer trigger the AttachmentIsUnsupported predicate.

For more information