Blocked attachments in Microsoft 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.

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 7Zip, 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, 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 7Zip, creates a compressed archive file that has a different file name extension. Outlook doesn’t recognise 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

File name extension File type
.ade Access Project Extension (Microsoft)
.adp Access Project (Microsoft)
.app Executable Application
.asp Active Server Page
.aspx Active Server Page Extended
.asx ASF Redirector file
.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
.htc HTML component file
.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)
.py Python script
.pyc Python script
.pyo Python script
.pyw Python script
.pyz Python script
.pyzw Python script
.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
.vhd Virtual Hard Disk
.vhdx Virtual Hard Disk Extended
.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