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.
Locate the attachment in the email message.
Right-click the attachment, and then click Copy.
Right-click the desktop, and then click Paste.
Right-click the pasted file, and then click Rename.
Rename the file to use the original file name extension, such as .exe.
The first four methods are designed for a beginning to intermediate computer user. If these methods do not work for you and you are comfortable with advanced troubleshooting, you can use the methods in the "Advanced troubleshooting" section.
You may find it easier to follow the steps if you print this article first. Because some of these methods contain steps to restart your computer.
Use one of the following methods to open an attachment that was blocked in Outlook:
You might want to ask the sender to save the attachment to a server or an FTP site that you can access. Ask the sender to send you a link to the attachment on the server or FTP site. You can click the link to access the attachment and save it on your computer.
If you need help using the server or FTP site, you can ask the sender for help, or you can contact the server administrator for more information.
If no server or FTP site is available to you, you can ask the sender to use a file compression utility, such as WinZip, to compress the file. This creates a compressed archive file that has a different file name extension. Outlook does not recognize these file name extensions as potential threats. Therefore, it does not block the new attachment.
When the sender resends the new attachment to you, you can save it on your computer, and then you can use the third-party file compression software to extract the attachment. If you need help using the third-party file compression software, see your product documentation.
If third-party file compression software is not available to you, you might want to request that the sender rename the attachment to use a file name extension that Outlook does not recognize as a threat. For example, an executable file that has the file name extension .exe could be renamed as a Word 97 file that has a .doc file name extension.
Ask the sender to resend the renamed attachment to you. After you receive the renamed attachment, you can save it to your computer and rename the file again to use the original file name extension.
Follow these steps to save the attachment and rename it to use the original file name extension:
If you use Outlook with a Microsoft Exchange server and the administrator has configured the Outlook security settings, the administrator might be able to help you. Ask the administrator to adjust the security settings on your mailbox to accept attachments such as the one that Outlook blocked.
If these methods did not work for you, and you are comfortable with advanced troubleshooting, please try the steps in the "Advanced troubleshooting" section.
If you are not comfortable with advanced troubleshooting, unfortunately this content is unable to help you any more. For your next steps, you might want to ask someone for help, or you might want to contact Support. For information about how to contact Support, please visit the following Microsoft Web site:
http://support.microsoft.com/contactus
If you do not use Outlook with an Exchange server or if the Exchange server administrator lets users change the Outlook attachment security behavior, use method 1: "Customize attachment security behavior."
If you use Outlook with an Exchange server and the Exchange Server administrator has disallowed changes to the Outlook attachment security behavior, use method 2: "Configure Outlook in an Exchange environment."
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
Important Before you can customize the attachment security behavior in Outlook 2000 SR1 and Microsoft Outlook 2000 SR1a, you must first apply either Microsoft Office 2000 Service Pack 2 or Microsoft Office 2000 Service Pack 3.
Follow these steps to modify the registry and change Outlook's attachment security behavior.
regedit
Microsoft Office Outlook 2016
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security
Microsoft Office Outlook 2013
HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Security
Microsoft Office Outlook 2010
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security
Microsoft Office Outlook 2007
HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Security
Microsoft Office Outlook 2003
HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Security
Microsoft Outlook 2002
HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security
Microsoft Outlook 2000
HKEY_CURRENT_USER\Software\Microsoft\Office\9.0\Outlook\Security
If the registry key exists, go to step 5.
If the registry key does not exist, follow these steps to create it:
HKEY_CURRENT_USER\Software\Microsoft
For Outlook 2013, type 15.0, and then press ENTER.
For Outlook 2010, type 14.0, and then press ENTER.
For Outlook 2007, type 12.0, and then press ENTER.
For Outlook 2003, type 11.0, and then press ENTER.
For Outlook 2002, type 10.0, and then press ENTER.
For Outlook 2000, type 9.0, and then press ENTER.
Level1Remove
.exe
To specify multiple file types, use the following format:
.exe;.com
When you start Outlook, you can open the file types that you specified in the registry.
Note We recommend that you enable only the file types that you have to have. If you rarely receive a particular file type, we recommend that you give Outlook temporary access to the file type that is in question. Then, reconfigure Outlook to block the file type by undoing the changes to the registry. For more information about how you can configure Outlook to block attachment file name extensions that Outlook does not block by default, click the following article number to view the article in the Microsoft Knowledge Base:
837388 How to configure Outlook to block additional attachment file name extensions
If you run Outlook in an Exchange environment, the Exchange server administrator can change the default attachment security behavior. For more information about how to configure Outlook in an Exchange environment, click the following article numbers to view the articles in the Microsoft Knowledge Base:
290499 Administrator information about e-mail security features
263297 Administrator information about the Outlook E-mail Security update: June 7, 2000
Attachments are divided into three groups based on their file name extension or file type. Outlook handles each group in a specific way.
The unsafe category represents any file name extension that may have script or code associated with it. You cannot open any attachment that has an unsafe file name extension. For a list of the unsafe file name extensions, see this Office support page. The following list describes how Outlook behaves when you receive or send an unsafe file attachment:
Can't open the item. Outlook blocked access to this potentially unsafe item.
Level 2 files are not unsafe. However, they do require more security than other attachments. When you receive a Level 2 attachment, Outlook prompts you to save the attachment to a disk. You cannot open the attachment in the e-mail message. By default, file name extensions are not associated with this group. However, if you use Outlook with an Exchange server and your mail is delivered to an Exchange mailbox, the Exchange server administrator can add file name extensions to the Level 2 list.
When you try to open an attachment that has a file name extension other than those in the Level 1 or the Level 2 list, Outlook prompts you to either open the file directly or save it to a disk. You can turn off future prompts for that file name extension if you clear the Always ask before opening this type of file check box.
Note If a program associates itself with a new file name extension, Outlook treats that file name extension as safe until you add the file name extension to the list of Level 1 or Level 2 file name extensions.
For example, if you install a program on your computer that uses files that have a .xyz file name extension, when you open an attachment that has a .xyz file name extension, the program opens and runs the attachment. By default, the .xyz file name extension does not appear on the Level 1 or the Level 2 list. Therefore, Outlook treats it as a safe file name extension. If you want Outlook to treat attachments that have the .xyz file name extension as unsafe, you must add the .xyz file name extension to the list of Level 1 file name extensions.