Blocked File Types and Extensions – Mailprotector Help Center

Mailprotector's CloudFilter email security blocks inbound and outbound emails containing high-risk executable file attachments with specific extensions such as .exe, .bat, .msi, and others to prevent virus spread, and users attempting to send these receive a bounce notification explaining the block and corrective actions.

Mailprotector blocks high-risk extensions from being relayed inbound or outbound through our security layers. If you/your users attempt to send a banned extension, they will receive the following response (bounce/NDR) with the following explanation and corrective actions.

A file you sent was blocked by CloudFilter™

You are trying to send an email message with a file attachment to a recipient protected by CloudFilter email security from Mailprotector®. The file attachment that you are trying to send contains a three-letter extension which makes this file "executable."

Computer viruses are often spread as programs attached to email messages. These messages usually trick the recipient into clicking on the file and "executing" the program. However, some are able to automatically execute themselves when an email message is merely previewed by the recipient. Because of this, the following file extensions are automatically blocked by CloudFilter:

Blocked Extensions


.ade	Access Project Extension
.mdb	Access Database
.adp	Access Project file
.mde	Access file
.bas	BASIC Program
.msc	Common Console Doc (Win2k)
.bat	DOS Batch File Script
.msi	Installer Program
.chm	Compiled HTML file
.msp	Windows Installer Patch file
.cmd	1st Reader External Command Menu
.mst	Windows Installer Transform file
.com	Command file (Program)
.pcd	P-Code Compiled Test Script
.cpl	Control Panel Module
.pif	Program Info file (Win 3.1)
.crt	Certificate file
.reg	Registration file
.exe	Executable file (Program)
.scr	Screensaver
.hlp	Windows Help file
.sct	FoxPro Form
.hta	HTML file
.shs	Shell Scrap file
.inf	Package Information file
.url	Internet Shortcut file
.ins	Install Script
.vbs	VisualBasic Program
.isp	Sign-up file (X-Internet)
.vbe	VisualBasic Related
.jsp	JavaScript
.wsf	Windows Script Component
.lnk	Shortcut file (Windows)
.wsh	Windows Script file
.wsc	Windows Script Host Settings file
.js	JavaScript

Question: How can I send my message?

Answer: The first option is to rename your file attachment. For example, you could rename your attachment to "filename.txt" with instructions in the body of your message as to what the appropriate extension should be. Another option is to compress your file(s) with an easy to use file compression utility.

Question: I'm having trouble with blocked attachments in Outlook also. How can I fix that?

Answer: Similar to the protection provided through CloudFilter, Outlook blocks dangerous file types and extensions. Visit Microsoft's knowledge base article on blocked attachments for more information.

Updated 9 years ago

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