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.
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.
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.
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.
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.
| 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 |