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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


Access Project Extension (Microsoft)


Access Project (Microsoft)


Executable Application


ClickOnce Deployment Manifest File


ClickOnce Application Reference File


Active Server Page


Active Server Page Extended


ASF Redirector File


BASIC Source Code


Batch Processing


Borland Graphics Interface


Windows Cabinet File


Internet Security Certificate File


Compiled HTML Help


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


Microsoft Help Workshop Application




Windows Control Panel Extension (Microsoft)


Certificate File


csh Script


DER Encoded X509 Certificate File


Microsoft Diagnostics Cabinet File


Executable File


FoxPro Compiled Source (Microsoft)


Windows Vista Gadget


Microsoft Program Group


Windows Help File


AppWizard Help project


Hypertext Application


HTML Component File


Information or Setup File


IIS Internet Communications Settings (Microsoft)


Optical Disk Media File System


IIS Internet Service Provider Settings (Microsoft)


Internet Document Set, Internet Translation


Java Archive


Java Network Launching Protocol


JavaScript Source Code


JScript Encoded Script File


UNIX Shell Script


Windows Shortcut File


Access Module Shortcut (Microsoft)


Access (Microsoft)


Access Diagram Shortcut (Microsoft)


Access Macro Shortcut (Microsoft)


Access Query Shortcut (Microsoft)


Access Report Shortcut (Microsoft)


Access Stored Procedures (Microsoft)


Access Table Shortcut (Microsoft)


Media Attachment Unit


Access View Shortcut (Microsoft)


Access Data Access Page (Microsoft)


Media Container Format


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


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


Access MDE Database File (Microsoft)


Access Add-in Data (Microsoft)


Access Workgroup Information (Microsoft)


Access Wizard Template (Microsoft)


Microsoft Management Console Snap-in Control File (Microsoft)


Microsoft Shell


Microsoft Shell


Microsoft Shell


Microsoft Shell


Microsoft Shell


Microsoft Shell


Windows Installer File (Microsoft)


Windows Installer Update


Windows SDK Setup Transform Script


Windows Update File


Office Profile Settings File


Open Software Description 


Visual Test (Microsoft)


Windows Program Information File (Microsoft)


Perl script


Developer Studio Build Log


Windows System File


Program File


Printer backup File


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


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


Python Script


Python Script


Python Script


Python Script


Python Script


Python Script


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


Windows Explorer Command


Windows Screen Saver


Windows Script Component, Foxpro Screen (Microsoft)


Windows Shortcut into a Document


Shell Scrap Object File


Desktop Theme File Settings


Temporary File/Folder


Internet Location


VBScript File or Any Visual Basic Source


VBScript Encoded Script File


Visual Basic Project File


VBScript Script File, Visual Basic for Applications Script


Virtual Hard Disk


Virtual Hard Disk Extended


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


Visio Workspace File (Microsoft)


Internet Printing File


Pinned Site Shortcut from Internet Explorer


Windows Script File


Windows Script Component


Windows Script File


Windows Script Host Settings File


Browser Applications


Excel Addin


Exchange Public Folder Shortcut

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