How can you get an email attachment that Outlook for Windows has blocked?
Outlook will automatically block email attachments with certain extensions. We’ve copied the full list of blocked extension below. Developers and IT people are the most likely to get frustrated by Outlook file blocks.
In many cases the blocked file is really plain text code or script which could be resent within an email message body instead of an attachment. The receiver just selects part of the message and makes a new file.
Here’s some of the file types that you might want to get past Outlook with some comments on alternative ways to send the file.
.asp an Active Server Page, commonly used on web sites. A plain text file.The more recent .aspx equivalent is not blocked.
.cer, crt Internet certificate. These are usually delivered by SSL providers via a .ZIP file.
.cmd or .bat Windows /DOS command file. These are plain text and usually short so they can be sent in a message body and easily recreated.
.js Javascript source code. Again, this is plain text and could be send in a message body instead.
.pl Perl script. Another plain text file.
.mdb .mda and other MS Access files. Use ZIP instead (most compress into a much smaller file).
.ps1 and other PowerShell scripts. Use plain text instead.
.reg – more plain text
.url a Internet link, put in a message body instead.
Most of these are blocked for good reason. Under no circumstances should you open a .exe attachment even from someone you trust.
But sometimes you’ll get an email with attachment that you need. How to bypass the Outlook block?
The easiest option is to ask the sender to resend the files in a different format (like ZIP or RAR), to a different email account or via an online file share. But assuming those options aren’t available.
WARNING: use any attachment you get after unblocking with extreme caution. Microsoft hasn’t blocked these attachments to be annoying, they are trying to protect their customers.
Make sure that the email attachment comes from the genuine sender and it’s not a spoofed email that the sender has no clue about.
You can’t direct change what Microsoft calls the ‘Level 1’ block list for Outlook attachments but you can manually exclude an extension from the current list.
The Outlook attachment blocks can be removed in the Registry at:
HKEY_CURRENT_USER\Software\Microsoft\Office\<version>\Outlook\Security
The <version> of Outlook is
- Outlook 2016
16.0
- Outlook 2013
15.0
- Outlook 2010
14.0
- Outlook 2007
12.0
- Outlook 2003
11.0
- Outlook 2002 (XP)
10.0
- Outlook 2000
9.0
For Outlook 2016 it’s
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security
Now add a String value Level1Remove
The data is a list of extensions you want UNblocked with a dot/period and a semi-colon to separate.
To Unblock just Access .MDB files use .mdb
To Unblock .mdb and .bat files use .mdb;.bat
After a registry change, restart Outlook and the blocked attachment is now available.
If you’ve made the registry change just to access a single attachment. Save the attachment to your computer (and check it for nasties) then remove the registry entry.
If you need to unblock occasionally, rename the key to disable it. That makes it easy to quickly restore in the future.
Outlook will ignore a registry entry with a name it doesn’t recognize.
Here’s a list of blocked attachments, as advised by Microsoft. There’s a search field at the top (depending on your browser).
File extension | File type |
---|---|
.ade | Microsoft Access project extension |
.adp | Microsoft Access project |
.app | Application file |
.asp | Active server page |
.bas | Microsoft Visual Basic class module |
.bat | Batch file |
.cer | Internet Security Certificate file |
.chm | Compiled HTML Help file |
.cmd | DOS CP/M command file, Microsoft Windows NT command script |
.cnt | Windows Help contents file |
.com | Microsoft MS_DOS program |
.cpl | Control Panel extension |
.crt | Security certificate |
.csh | Script file |
.der | DER Encoded X509 certificate file |
.exe | Executable file |
.fxp | Microsoft Visual FoxPro compiled program |
.gadget | Windows Gadget |
.grp | Windows program group file |
.hlp | Help file |
.hpj | Help project file |
.hta | HTML program |
.inf | Information or setup file |
.ins | Internet Naming Service |
.isp | Internet Communication settings |
.its | Internet Document Set file |
.jar | JAVA archive file |
.js | JavaScript source code |
.jse | JScript Encoded script file |
.ksh | UNIX Shell script file |
.lnk | Windows shortcut |
.mad | Microsoft Access module shortcut |
.maf | Microsoft Access shortcut |
.mag | Microsoft Access diagram shortcut |
.mam | Microsoft Access macro shortcut |
.maq | Microsoft Access query shortcut |
.mar | Microsoft Access report shortcut |
.mas | Microsoft Access stored procedures |
.mat | Microsoft Access table shortcut |
.mau | Media attachment unit |
.mav | Microsoft Access view shortcut |
.maw | Microsoft Access data access page |
.mcf | Manifest configuration file |
.mda | Microsoft Access add-in program |
.mdb | Microsoft Access program |
.mde | Microsoft Access MDE database file |
.mdt | Microsoft Access data file |
.mdw | Microsoft Access workgroup |
.mdz | Microsoft Access wizard program |
.msc | Microsoft Common Console document |
.msh | Windows PowerShell script helper |
.msh1 | Windows PowerShell script helper |
.msh2 | Windows PowerShell script helper |
.mshxml | Windows PowerShell script helper |
.msh1xml | Windows PowerShell script helper |
.msh2xml | Windows PowerShell script helper |
.msi | Windows Installer package |
.msp | Windows Installer update package file |
.mst | Visual Test source file |
.ops | Microsoft Office profile settings file |
.osd | Open software description file |
.pcd | Microsoft Visual Test compiled script |
.pif | Windows program information file |
.pl | Perl script file |
.plg | Developer Studio build log |
.prf | Outlook profile file |
.prg | Program source file |
.ps1 | Windows PowerShell |
.ps1xml | Windows PowerShell |
.ps2 | Windows PowerShell |
.ps2xml | Windows PowerShell |
.psc1 | Windows PowerShell |
.psc2 | Windows PowerShell |
.pst | Microsoft Outlook personal folder file |
.reg | Registration entries, Registry data file |
.scf | Windows Explorer command file |
.scr | Windows screen saver |
.sct | Windows script component |
.shb | Windows shortcut to a document |
.shs | Shell Scrap object file |
.tmp | Temporary file or folder |
.url | Uniform Resource Locator (Internet shortcut) |
.vb | Microsoft Visual Basic Scripting Edition (VBScript) file |
.vbe | VBScript Encoded script file |
.vbp | Visual Basic project file |
.vbs | VBScript script file, Visual Basic for Applications script file |
.vsmacros | Microsoft Visual Studio .NET binary-based macro project file |
.vsw | Microsoft Visio workspace file |
.ws | Windows script file |
.wsc | Windows script component |
.wsf | Windows script file |
.wsh | Windows Script Host settings file |
.xbap | XAML browser application |
.xnk | Microsoft Exchange public folder shortcut |