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Blocked File Attachment Types on CSUChico E-Mail


As a result of recent viruses and concerns over the security of campus computers, the campus e-mail servers are blocking certain file attachments. Files with any of the extensions listed on this page will be removed from email messages, and the sender will receive a notification message from the mail server.


What happens to the message if an attachment is blocked?

If the server encounters a file type on it's blocked list or the virus scanner detects a virus in the file,the message is delivered, but the attachment is removed and the message is appended with the following text to warn the recipient:

Notification Email
An attachment to this email was removed because it was found to contain a
virus, worm, disallowed file type or other malicious software. If the
attachment was a legitimate file that you were expecting, you should
arrange an alternate delivery method with the sender.
For a complete list of the file types that are blocked, or for more
information, please see:
IT Support Services - 898-HELP(4357)

.zip Files Now Allowed

.zip files were previously in the list of blocked attachment types, but improvements in our virus scanners now allow us to scan files within .zip archives.  This makes the .zip file itself safe to send or receive and because of this it is no longer blocked.  If the .zip file contains a blocked file type or an infected file, the entire .zip archive will be removed from the email.

The scanner is not able to scan .zip archives that have been password protected.  They will be passed through, along with a warning message that the files contained have not been scanned.  If you need to send or receive a file type on the blocked list, you can protect the .zip file with a password and supply the password in your message so the recipient can open the file.  Instructions for password protecting zip files are available for Mac and PC.

Renaming The File Type No Longer Bypasses Filters

The new virus scanning and attachment blocking filters are also able to determine the real file type of an attachment without relying on it's extension name (.zip, .exe, etc.). Previously, if you needed to send or receive a file type that was normally blocked, you could rename the file extension in order to "fool" the attachment removal and allow the file through. Thus you could rename the file "myscript.exe" to "" and send the file through. You would then inform your recipient to rename the file to "myscript.exe" before they tried to open it. This method will no longer work. In order to get legitimate files past the filters, we have an alternate method of using a password protected .zip file.

Working With Password Protected or Encrypted .zip Files to Bypass The Filters

Our filters are unable to scan files within a password protected .zip archive. When the filters encounter a protected .zip file, a warning message is appended to the original message and is passed through with the attachment in tact. If you need to send or receive a file type on the blocked list, you can protect the .zip file with a password and supply the password in your message in order for your recipient to open the file. If you need to receive one of these files, you can forward instructions for your sender to do the same.

Common Blocked File Types

Type Reason for Being Blocked
rar Possible virus hidden in RAR Archive
com Windows/DOS Executable
exe Windows/DOS Executable
scr Possible virus hidden in a screensaver
pif Possible MS-Dos program shortcut attack
bat Possible malicious batch file script
cmd Possible malicious batch file script
vb[usrv:es] Possible Microsoft Visual Basic script attack
Possible Microsoft Windows Script Host attack
hta Possible Microsoft HTML archive attack
sys Windows/DOS system file

Full List of Blocked File Types

Extension File Type
.386 Virtual Device Driver (Windows 386 enhanced mode)
.3gr VGA Graphics driver/configuration files
.add Adapter Drive File
.ade Microsoft Access project extension
.asp Active Server Page
.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 Database Index
.dll Dynamic Link Library
.exe Program
.fon Font File
.hlp Help file
.hta HTML program
.inf Setup Information
.ins Internet Naming Service
.isp Internet Communication settings
.js JScript file
.jse Jscript Encoded Script file
.lnk Shortcut
.mdb Microsoft Access program
.mde Microsoft Access MDE databaset
.msc Microsoft Common Console Document
.msi Microsoft Windows Installer package
.msp Microsoft Windows Installer patch
.mst Microsoft Windows Installer transform; Microsoft Visual Test source file
.ocx Microsoft Object Linking
.pcd Images CD Creator Corel Adaptec
.pif Shortcut to MS-DOS program
.reg Registration entries
.scr Screen saver
.sct Windows Script Component
.shs Shell Scrap object
.shb Shell Scrap object
.url Internet shortcut
.vb VBScript file
.vbe VBScript Encoded script file
.vbs VBScript file
.vxd Microsoft Windows Virtual Device Diver
.wsc Windows Script Component
.wsf Windows Script file
.wsh Windows Script Host Settings file

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This page is maintained by IT Support Services at CSU, Chico. Please send any feedback, questions or corrections to

Contact ITSS

Students, Faculty and Staff Support
Walk-up: MLIB 142
Phone: 898-HELP(4357)
Service Desk Hours

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