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.

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 ...

Under Virus & threat protection settings, select Manage settings, and then under Exclusions, select Add or remove exclusions. Select Add an exclusion, and then select from files, folders, file types, or process. A folder exclusion will apply to all subfolders within the folder as well.

The Attachment Manager is included in Microsoft Windows to help protect your computer from unsafe attachments that you might receive with an e-mail message and from unsafe files that you might save from the Internet.

To learn more about how malware works and how to prevent malware infection, see Help prevent malware infection on your PC.. What do I do if I think the system made a mistake? If your organization uses Microsoft Defender for Office 365 and a file is blocked that you think should not be, you'll need some help from a Microsoft 365 administrator who can research the issue and, potentially, unblock ...

Making changes starts or disables the ability to create trust documents that protects your computer and your organization's network from possible malicious code in active content. Click the File tab. Click Options. Select Trust Center, and then Trust Center Settings. Click Trusted Documents.

You can report a site as unsafe in Microsoft Edge. If you visit a site that you think SmartScreen should warn you about in the future, you can report it to Microsoft. From the site you believe is unsafe, select Settings and more > Help and feedback > Report unsafe website and follow the directions.

Outlook blocked access to the following potentially unsafe attachments: filename. The attachments that are affected by this issue are fairly uncommon. They are typically created by custom solutions by using Extended MAPI or the Outlook object model to add functionality to a Microsoft Exchange mailbox or to a local set of Outlook folders.

What is external content, and why are Web beacons a potential threat? External content is any content linked from the Internet or an intranet to a workbook or presentation. Some examples of external content are images, linked media, data connections, and templates. Hackers can use external content as Web beacons.

A hacker (malicious user) might have renamed the file with the intent of misleading you to open it in Excel. An issue with a file name extension might occur when a workbook that you are trying to open is unreadable and the contents no longer resemble the expected file format.