Blocked Attachment Types

For security purposes, a number of attachment types are blocked by default by Microsoft Office 365.  These types are those where the risk of malicious content is significant - and the legitimate use of the file types are limited.  The list of attachment types are below.  They are subject to change without notice as risk conditions warrant.

Microsoft Office - Macro Enabled File Types

• .docm, (Word)
• .ppsm, .pptm .sldm (Powerpoint)
• .xlam, .xlm (Excel)

Executable Content Types:

• .com
• .dll
• .dos
• .exe
• .jar
• .obj
• .os2
• .pif
• .rar
• .vbe
• .vxd
• .w16

Other file types:

• .ace (extremely uncommon compressed file type)
• .ani
• .app
• .reg (Microsoft Registry File)
• .w16