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Blocked attachments in Outlook

One of the most common ways of transmitting computer viruses is through file attachments. To help protect you and your recipients against computer viruses, Outlook blocks the sending and receiving of certain types of files (such as .exe and certain database files) as attachments. If you need to send one of these file types to an email recipient, we recommend using OneDrive and sending the recipient a link to the file instead.

Note: If you're using a Microsoft Exchange account, your email server administrator can unblock certain file types. Contact your administrator for more assistance.

Share your files safely

There are several ways to send and receive a blocked file. You can save the file to the cloud and send a link to the file, use a file compression utility like WinZip, or even rename the file with another extension, then have your recipient change the name back to the original name after they receive the file.

  • Save the file to the cloud
    If you need to send a file that's blocked by Outlook, the simplest way to send your file is to upload it to OneDrive or a secure network share server such as SharePoint. Then send a link to the file. If you need to receive a blocked file, ask the sender to upload the file to OneDrive or SharePoint and send you a link. Once you receive the link, you can open the file location and download the file.
     

    Note: For OneDrive and OneDrive for Business, you'll need to ask the sender to only send you a link to the file rather than attach the file to the email using OneDrive. To obtain a sharing link in OneDrive, highlight the file and choose Get Link in the menu bar.

  • Use a file compression utility   
    Using a compression utility, such as WinZip, creates a compressed archive file that has a different file name extension. Outlook doesn’t recognize these file name extensions as potential threats. Therefore, it doesn’t block the new attachment. Many third-party compression utilities are available. You can right-click any file in Windows 7, Windows 8, or Windows 10 and select Send to compressed (zipped) folder. This creates a file with the same name as the original file, but the extension of .zip.

  • Rename the file   
    You can rename the file (or request that the sender rename the file) to use an extension that Outlook doesn't block. For example, you can rename file.exe to file.docx. Once the renamed file is sent (or received), save it and rename it with the original extension using the following steps.

  1. Locate the attachment in the email message.

  2. Right-click the attachment, and then click Copy.

  3. Right-click the desktop, and then click Paste.

  4. Right-click the pasted file, and then click Rename.

  5. Rename the file to use the original file name extension, such as .exe.

Blocked file types in Outlook

If you use a Microsoft Exchange Server account and the Exchange Server administrator has configured your Outlook security settings, your administrator might be able to help you. Ask the administrator to adjust the security settings on your mailbox to accept attachments that Outlook blocked.

If you don’t use an Exchange Server account, there is an advanced procedure that you can use to unblock some file types. This procedure involves editing the registry in Windows. For more information about unblocking attachment file types, see the Microsoft Support article about blocked attachments in Outlook.

File types blocked in Outlook

File name extension

File type

.ade

Access Project Extension (Microsoft)

.adp

Access Project (Microsoft)

.app

Executable Application

.asp

Active Server Page

.bas

BASIC Source Code

.bat

Batch Processing

.cer

Internet Security Certificate File

.chm

Compiled HTML Help

.cmd

DOS CP/M Command File, Command File for Windows NT

.cnt

Microsoft Help Workshop Application

.com

Command

.cpl

Windows Control Panel Extension (Microsoft)

.crt

Certificate File

.csh

csh Script

.der

DER Encoded X509 Certificate File

.diagcab

Microsoft Support diagnostic tools

.exe

Executable File

.fxp

FoxPro Compiled Source (Microsoft)

.gadget

Windows Vista gadget

.grp

Microsoft program group

.hlp

Windows Help File

.hpj

AppWizard Help project

.hta

Hypertext Application

.inf

Information or Setup File

.ins

IIS Internet Communications Settings (Microsoft)

.isp

IIS Internet Service Provider Settings (Microsoft)

.its

Internet Document Set, Internet Translation

.jar

Java Archive

.jnlp

Java Network Launch Protocol

.js

JavaScript Source Code

.jse

JScript Encoded Script File

.ksh

UNIX Shell Script

.lnk

Windows Shortcut File

.mad

Access Module Shortcut (Microsoft)

.maf

Access (Microsoft)

.mag

Access Diagram Shortcut (Microsoft)

.mam

Access Macro Shortcut (Microsoft)

.maq

Access Query Shortcut (Microsoft)

.mar

Access Report Shortcut (Microsoft)

.mas

Access Stored Procedures (Microsoft)

.mat

Access Table Shortcut (Microsoft)

.mau

Media Attachment Unit

.mav

Access View Shortcut (Microsoft)

.maw

Access Data Access Page (Microsoft)

.mcf

Media Container Format

.mda

Access Add-in (Microsoft), MDA Access 2 Workgroup (Microsoft)

.mdb

Access Application (Microsoft), MDB Access Database (Microsoft)

.mde

Access MDE Database File (Microsoft)

.mdt

Access Add-in Data (Microsoft)

.mdw

Access Workgroup Information (Microsoft)

.mdz

Access Wizard Template (Microsoft)

.msc

Microsoft Management Console Snap-in Control File (Microsoft)

.msh

Microsoft Shell

.msh1

Microsoft Shell

.msh2

Microsoft Shell

.mshxml

Microsoft Shell

.msh1xml

Microsoft Shell

.msh2xml

Microsoft Shell

.msi

Windows Installer File (Microsoft)

.msp

Windows Installer Update

.mst

Windows SDK Setup Transform Script

.msu

Windows Update file

.ops

Office Profile Settings File

.osd

Open Software Description 

.pcd

Visual Test (Microsoft)

.pif

Windows Program Information File (Microsoft)

.pl

Perl script

.plg

Developer Studio Build Log

.prf

Windows System File

.prg

Program File

.printerexport

Printer backup file

.ps1

Windows PowerShell

.ps1xml

Windows PowerShell

.ps2

Windows PowerShell

.ps2xml

Windows PowerShell

.psc1

Windows PowerShell

.psc2

Windows PowerShell

.psd1

Windows PowerShell

.psdm1

Windows PowerShell

.pst

MS Exchange Address Book File, Outlook Personal Folder File (Microsoft)

.reg

Registration Information/Key for W95/98, Registry Data File

.scf

Windows Explorer Command

.scr

Windows Screen Saver

.sct

Windows Script Component, Foxpro Screen (Microsoft)

.shb

Windows Shortcut into a Document

.shs

Shell Scrap Object File

.theme

Desktop theme file settings

.tmp

Temporary File/Folder

.url

Internet Location

.vb

VBScript File or Any Visual Basic Source

.vbe

VBScript Encoded Script File

.vbp

Visual Basic project file

.vbs

VBScript Script File, Visual Basic for Applications Script

.vsmacros

Visual Studio .NET Binary-based Macro Project (Microsoft)

.vsw

Visio Workspace File (Microsoft)

.webpnp

Internet printing file

.website

Pinned site shortcut from Internet Explorer

.ws

Windows Script File

.wsc

Windows Script Component

.wsf

Windows Script File

.wsh

Windows Script Host Settings File

.xbap

Browser applications

.xll

Excel add-in

.xnk

Exchange Public Folder Shortcut

File types blocked in Outlook 2007

File name extension

File type

.ade

Access Project Extension (Microsoft)

.adp

Access Project (Microsoft)

.app

Executable Application

.asp

Active Server Page

.bas

BASIC Source Code

.bat

Batch Processing

.cer

Internet Security Certificate File

.chm

Compiled HTML Help

.cmd

DOS CP/M Command File, Command File for Windows NT

.cnt

Help file index

.com

Command

.cpl

Windows Control Panel Extension (Microsoft)

.crt

Certificate File

.csh

csh Script

.der

DER Encoded X509 Certificate File

.exe

Executable File

.fxp

FoxPro Compiled Source (Microsoft)

.gadget

Windows Vista gadget

.hlp

Windows Help File

.hpj

Project file used to create Windows Help File

.hta

Hypertext Application

.inf

Information or Setup File

.ins

IIS Internet Communications Settings (Microsoft)

.isp

IIS Internet Service Provider Settings (Microsoft)

.its

Internet Document Set, Internet Translation

.js

JavaScript Source Code

.jse

JScript Encoded Script File

.ksh

UNIX Shell Script

.lnk

Windows Shortcut File

.mad

Access Module Shortcut (Microsoft)

.maf

Access (Microsoft)

.mag

Access Diagram Shortcut (Microsoft)

.mam

Access Macro Shortcut (Microsoft)

.maq

Access Query Shortcut (Microsoft)

.mar

Access Report Shortcut (Microsoft)

.mas

Access Stored Procedures (Microsoft)

.mat

Access Table Shortcut (Microsoft)

.mau

Media Attachment Unit

.mav

Access View Shortcut (Microsoft)

.maw

Access Data Access Page (Microsoft)

.mda

Access Add-in (Microsoft), MDA Access 2 Workgroup (Microsoft)

.mdb

Access Application (Microsoft), MDB Access Database (Microsoft)

.mde

Access MDE Database File (Microsoft)

.mdt

Access Add-in Data (Microsoft)

.mdw

Access Workgroup Information (Microsoft)

.mdz

Access Wizard Template (Microsoft)

.msc

Microsoft Management Console Snap-in Control File (Microsoft)

.msh

Microsoft Shell

.msh1

Microsoft Shell

.msh2

Microsoft Shell

.mshxml

Microsoft Shell

.msh1xml

Microsoft Shell

.msh2xml

Microsoft Shell

.msi

Windows Installer File (Microsoft)

.msp

Windows Installer Update

.mst

Windows SDK Setup Transform Script

.ops

Office Profile Settings File

.osd

Application virtualized with Microsoft SoftGrid Sequencer

.pcd

Visual Test (Microsoft)

.pif

Windows Program Information File (Microsoft)

.plg

Developer Studio Build Log

.prf

Windows System File

.prg

Program File

.pst

MS Exchange Address Book File, Outlook Personal Folder File (Microsoft)

.reg

Registration Information/Key for W95/98, Registry Data File

.scf

Windows Explorer Command

.scr

Windows Screen Saver

.sct

Windows Script Component, Foxpro Screen (Microsoft)

.shb

Windows Shortcut into a Document

.shs

Shell Scrap Object File

.ps1

Windows PowerShell

.ps1xml

Windows PowerShell

.ps2

Windows PowerShell

.ps2xml

Windows PowerShell

.psc1

Windows PowerShell

.psc2

Windows PowerShell

.tmp

Temporary File/Folder

.url

Internet Location

.vb

VBScript File or Any VisualBasic Source

.vbe

VBScript Encoded Script File

.vbp

Visual Basic project file

.vbs

VBScript Script File, Visual Basic for Applications Script

.vsmacros

Visual Studio .NET Binary-based Macro Project (Microsoft)

.vsw

Visio Workspace File (Microsoft)

.ws

Windows Script File

.wsc

Windows Script Component

.wsf

Windows Script File

.wsh

Windows Script Host Settings File

.xnk

Exchange Public Folder Shortcut

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