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.
If you attempt to email a blocked file type you will receive an email similar to what is shown below.
----Sample-Message----
From: Postmaster
Sent: Tuesday, February 16, 2021 11:16 AM
To: email@microsoftoffice365.com
Subject: Undeliverable message
This message was created automatically by mail delivery software. Your email message was not delivered to the intended recipients because malware was detected.
— Additional Information ---:
Subject: Your Email Subject Here
Sender: you@salisbury.edu
Time received: 2/16/2021 4:15:54 PM
Message ID:<######>
Detections found:
filename.filetype
File types blocked in Outlook
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 |