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Office 365 (Outlook on the Web) - Blocked File Attachment Types
Outlook on the Web by default blocks the attachment file types listed below.
The following document types may be blocked from being opened in Outlook Web App. A possible workaround is to use the Outlook desktop user (either on Mac or Windows) to download these blocked attachments. Please use caution when attempting to open a file attachment from an unexpected source.
| Extension | File Type |
| .asp | Active Server Page |
| .aspx | Active Server Page Extended |
| .apk | Android Package File |
| .ani | Animated Mouse Cursors |
| .ace | Archive File Format |
| .arj | arj compressed file |
| .bas | BASIC Source Code |
| .bat | Batch Processing |
| .cab | Cabinet archive file |
| .crt | Certificate File |
| .com | Command |
| .chm | Compiled HTML Help |
| .xz | Compressed archive |
| .z | Compressed archive |
| .csh | csh Script |
| .dex | Dalvik executable format |
| .lha | Data compression file format |
| .lzh | Data compression file format |
| .deb | Debian package format |
| .der | DER Encoded X509 Certificate File |
| .plg | Developer Studio Build Log |
| .sys | Device driver file |
| .vxd | Device driver file |
| .cer | Digital Certificate |
| .crt | Digital Certificate |
| .der | Digital Certificate |
| .img | Disk images |
| .iso | Disk images |
| .cmd | DOS CP/M Command File, Command File for Windows NT |
| .dll | Dynamic link library |
| .elf | Executable and linkable format |
| .app | Executable Application |
| .exe | Executable File |
| .xml | Extensible Markup Language |
| .fxp | FoxPro Compiled Source (Microsoft) |
| .hta | Hypertext Application |
| .inf | Information or Setup File |
| .its | Internet Document Set, Internet Translation |
| .url | Internet Location |
| .cer | Internet Security Certificate File |
| .jar | Java File |
| .jnlp - | Java File |
| .js | JavaScript Source Code |
| .jse | JScript Encoded Script File |
| .lib | Linker input file |
| .macho | Mach object file format |
| .kext | macOS drivers |
| .mau | Media Attachment Unit |
| .mhtml - | MIME Html |
| .prg | Program File |
| .py | Python File |
| .pyc | Python File |
| .pyo | Python File |
| .pyw | Python File |
| .pyz | Python File |
| .pyzw | Python File |
| .rev | RAR Recovery volume set |
| .reg | Registration Information/Key for W95/98, Registry Data File |
| .shs | Shell Scrap Object File |
| .tmp | Temporary File/Folder |
| .appcontent-ms | Third-party Application |
| .cnt | Third-party Application |
| .diagcab | Third-party Application |
| .grp | Third-party Application |
| .hpj | Third-party Application |
| .mcf | Third-party Application |
| .msu | Third-party Application |
| .pl | Third-party Application |
| .printerexport | Third-party Application |
| .settingcontent-ms | Third-party Application |
| .theme | Third-party Application |
| .uif | Third-party Application |
| .vbp | Third-party Application |
| .webpnp | Third-party Application |
| .website | Third-party Application |
| .xbap | Third-party Application |
| .xll | Third-party Application |
| .xnk | Third-party Application |
| .ksh | UNIX Shell Script |
| .vbe | VBScript Encoded Script File |
| .vb | VBScript File or Any Visual Basic Source |
| .vbs | VBSript Script File, Visual Basic for Applications Script |
| .vst | Virtual Studio Technology |
| .msix | Windows app package |
| .scf | Windows Explorer Command |
| .hlp | Windows Help File |
| .msi | Windows Installer File |
| .msp | Windows Installer Update |
| .cdxml | Windows PowerShell |
| .ps1 | Windows PowerShell |
| .ps1xml | Windows PowerShell |
| .ps2 | Windows PowerShell |
| .ps2xml | Windows PowerShell |
| .psc1 | Windows PowerShell |
| .psc2 | Windows PowerShell |
| .psd1 | Windows PowerShell |
| .psdm1 | Windows PowerShell |
| .pssc | Windows PowerShell |
| .scr | Windows Screen Saver |
| .wsc | Windows Script Component |
| .ws | Windows Script File |
| .wsf | Windows Script File |
| .wsh | Windows Script Host Settings File |
| .mst | Windows SDK Setup Transform Script |
| .lnk | Windows Shortcut File |
| .shb | Windows Shortcut into a Document |
| .prf | Windows System File |
| .gadget | Windows Vista Gadget |
| .library - | Third-party Application |
| Microsoft Extensions | File Type |
| .maf | Access |
| .mda | Access Add-in , MDA Access 2 Workgroup |
| .mdt | Access Add-in Data |
| .mdb | Access Application , MDB Access Database |
| .maw | Access Data Access Page |
| .mag | Access Diagram Shortcut |
| .mam | Access Macro Shortcut |
| .mde | Access MDE Database File |
| .mad | Access Module Shortcut |
| .adp | Access Project |
| .ade | Access Project Extension |
| .maq | Access Query Shortcut |
| .mar | Access Report Shortcut |
| .mas | Access Stored Procedures |
| .mat | Access Table Shortcut |
| .mav- | Access View Shortcut |
| .mdz | Access Wizard Template |
| .mdw | Access Workgroup Information |
| .ins | IIS Internet Communications Settings |
| .isp | IIS Internet Service Provider Settings |
| .appx | Microsoft AppX Application Package |
| .appref-ms | Microsoft Component |
| .udl | Microsoft Component |
| .wsb | Microsoft Component |
| .msc | Microsoft Management Console Snap-in Control File |
| .msh | Microsoft Shell |
| .msh1 | Microsoft Shell |
| .msh1xml | Microsoft Shell |
| .msh2 | Microsoft Shell |
| .msh2xml | Microsoft Shell |
| .mshxml | Microsoft Shell |
| .docm | Microsoft Word Macro Enabled Document |
| .pst | MS Exchange Address Book File, Outlook Personal Folder File |
| .ops | Office Profile Settings File |
| .ppa | PowerPoint add-in |
| .ppam | PowerPoint add-in |
| .vss | Visio Stencil |
| .vsw | Visio Workspace File |
| .vsmacros | Visual Studio .NET Binary-based Macro Project |
| .pcd- | Visual Test |
| .cpl | Windows Control Panel Extension |
| .pif | Windows Program Information File |
| .sct | Windows Script Component, Foxpro Screen |