Santa Clara County ARES/RACES
Home Operations Data > E-mail Training & Events Reference FAQ

E-mail Blocked Filename Extensions

Overview   |  Blocked Extensions  |   Requesting Additions or Deletions

 

Overview

A variety of file types are dangerous for transmission via e-mail because they are executable programs and/or have the potential to damage the recipient's machine if opened. These file types are commonly identified by their filename extensions. Files with these extensions will be blocked by our e-mail servers.

Of course, the e-mail sender can simply change the filename to something with a different extension to avoid being blocked. But, by changing the extension, the recipient's machine will not know how to open or run the file, which protects it from inadvertent execution of a potentiall harmful file. The recipient can change the extension back to the original value to open or run the file. The recipient should only do so for files that they trust to be virus free.

 

Blocked Extensions

Extension Description
ade Microsoft Access Project Extension
adp Microsoft Access Project
app Mac OS X executable application program
asf Microsoft Advanced Streaming Format file
asx Windows Media Audio / Video
bas Microsoft Visual Basic class module
bat Batch file
chm Compiled HTML Help file
cmd Microsoft Windows NT Command script
com Microsoft MS-DOS program
cpl Control Panel extension
crt Security certificate
dbx Microsoft Visual Foxpro Table
dll Dynamic link library
exe Program
gadget Microsoft Windows Desktop Gadget file
hlp Windows Help file
hta HTML Application
hto Setup Information
inf Setup Information File
ins Internet Communications Settings
isp Internet Communications Settings
jar Java program
js JScript file
jse JScript Encoded Script file
lib Static link library
lnk Shortcut
mda Microsoft Access Add-in
mdb Microsoft Access program
mde Microsoft Access MDE database
mdz Microsoft Access Wizard template
msc Microsoft Common Console document
msi Microsoft Windows Installer package
msp Microsoft Windows Installer patch
mst Microsoft Windows Installer transform; Visual Test source file
nch Outpost Express Folder file
ocx Microsoft object linking and embedding files
ops Office XP settings
pcd Photo CD image; Microsoft Visual compiled script
pif Shortcut to MS-DOS program
pl Perl Script
prf Microsoft Outlook profile settings
py Python Script
pyc Python Compiled Script
pyo Python Compiled Optimized Script
reg Windows Registry file
scf Windows Explorer command
scr Screen saver
sct Windows Script Component
sh Shell script
shb Shell Scrap object
shs Shell Scrap object
sys Microsoft operating system or device driver files
url Uniform Resource Locator (Internet shortcut)
vb VBScript file
vbe VBScript Encoded script file
vbs VBScript file
wmd Windows Media Download package
wms Windows Media Player Skin
wmz Compressed Windows Media Player Skin
ws Windows Script Component
wsc Windows Script Component
wsf Windows Script file
wsh Windows Script Host Settings file

 

Requesting Additions or Deletions

To request that a filename extension be added or removed from the list of blocked extensions, please submit the extension name, description and reason for the change to the scc-email Yahoo group.

 

 


If you have E-mail Networking Information that you would like to have included here,
please contact the Webmaster, Phil Henderson

Web Site Home Page

This page was last updated 06-Oct-2017