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You may receive an "Outlook blocked access to the following potentially unsafe attachments" message in Outlook
Article ID: 829982 - View products that this article applies to.
When you receive an e-mail in Microsoft Outlook that contains an attachment, you might receive the following message at the top of the message or of the Reading Pane:
All versions of Outlook since Outlook 2000 Service Release 1 (SR1) include a security feature that blocks attachments that might put your computer at risk for viruses or other threats. Although Outlook blocks access to the attachment, the attachment still exists in the e-mail message.
Outlook blocked access to the following potentially unsafe attachments: 
This article describes methods that you can use if you have to open an attachment that is blocked in Outlook. Additionally, this article contains information about the kinds of attachments that Outlook blocks.
If Outlook blocks an attachment, you cannot save, delete, open, print, or otherwise work with the attachment in Outlook. However, you can use one of these methods to access the attachment more safely.
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.
General troubleshootingUse one of the following methods to open an attachment that was blocked in Outlook:
Method 1: Use a file share to access the attachmentYou 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.
Method 2: Use a file compression utility to change the file name extensionIf 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.
For a list of third-party compression products, click the following article number to view the Microsoft Knowledge Base article:
(http://support.microsoft.com/kb/291637/ )Attachments are not compressed by Outlook 2002
Method 3: Rename the file to have a different file name extensionIf 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:
Method 4: Ask the Exchange server administrator to change the security settingsIf 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:
Advanced troubleshootingIf 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."
Method 1: Customize attachment security behaviorImportant 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:
322756Important 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.
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
Follow these steps to modify the registry and change Outlook's attachment security behavior.
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:
(http://support.microsoft.com/kb/837388/ )How to configure Outlook to block additional attachment file name extensions
Method 2: Configure Outlook in an Exchange environmentIf 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:
(http://support.microsoft.com/kb/290499/ )Administrator information about e-mail security features
(http://support.microsoft.com/kb/263297/ )Administrator information about the Outlook E-mail Security update: June 7, 2000
Attachment BehaviorAttachments are divided into three groups based on their file name extension or file type. Outlook handles each group in a specific way.
Level 1 (Unsafe)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, visit the following Microsoft Web site:
http://office.microsoft.com/en-us/outlook/HA012299521033.aspxThe following list describes how Outlook behaves when you receive or send an unsafe file attachment:
Level 2Level 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.
Other AttachmentsWhen 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.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
284414For more information about the Level1Add registry key, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/284414/ )The recipient receives an "Outlook blocked access to the following potentially unsafe attachments" error message when you send an e-mail message that contains a shortcut to a file in Outlook
312834For more information about blocked attachments in Outlook, visit the following Microsoft Office Online Web site:
(http://support.microsoft.com/kb/312834/ )The Level1Add registry key is missing from Outlook 2002
(http://support.microsoft.com/kb/926512/ )Information for administrators about e-mail security settings in Outlook 2007
Article ID: 829982 - Last Review: September 20, 2011 - Revision: 12.0