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.


From: Postmaster

Sent: Tuesday, February 16, 2021 11:16 AM


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


Time received: 2/16/2021 4:15:54 PM

Message ID:<######>

Detections found:


File types blocked in Outlook

File name extension

File type



Access Project Extension (Microsoft)


Access Project (Microsoft)


Executable Application



Active Server Page


Active Server Page Extended


ASF Redirector file


BASIC Source Code


Batch Processing


Internet Security Certificate File


Compiled HTML Help


DOS CP/M Command File, Command File for Windows NT


Microsoft Help Workshop Application




Windows Control Panel Extension (Microsoft)


Certificate File


csh Script


DER Encoded X509 Certificate File


Microsoft Support diagnostic tools




Executable File


FoxPro Compiled Source (Microsoft)


Windows Vista gadget


Microsoft program group



Windows Help File


AppWizard Help project


Hypertext Application


HTML component file




Information or Setup File


IIS Internet Communications Settings (Microsoft)


IIS Internet Service Provider Settings (Microsoft)


Internet Document Set, Internet Translation


Java Archive


Java Network Launch Protocol


JavaScript Source Code


JScript Encoded Script File


UNIX Shell Script


Windows Shortcut File


Access Module Shortcut (Microsoft)


Access (Microsoft)


Access Diagram Shortcut (Microsoft)


Access Macro Shortcut (Microsoft)


Access Query Shortcut (Microsoft)


Access Report Shortcut (Microsoft)


Access Stored Procedures (Microsoft)


Access Table Shortcut (Microsoft)


Media Attachment Unit


Access View Shortcut (Microsoft)


Access Data Access Page (Microsoft)


Media Container Format


Access Add-in (Microsoft), MDA Access 2 Workgroup (Microsoft)


Access Application (Microsoft), MDB Access Database (Microsoft)


Access MDE Database File (Microsoft)


Access Add-in Data (Microsoft)


Access Workgroup Information (Microsoft)


Access Wizard Template (Microsoft)


Microsoft Management Console Snap-in Control File (Microsoft)


Microsoft Shell


Microsoft Shell


Microsoft Shell


Microsoft Shell


Microsoft Shell


Microsoft Shell


Windows Installer File (Microsoft)


Windows Installer Update


Windows SDK Setup Transform Script


Windows Update file


Office Profile Settings File


Open Software Description 


Visual Test (Microsoft)


Windows Program Information File (Microsoft)


Perl script


Developer Studio Build Log






Windows System File


Program File


Printer backup file


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


Windows PowerShell


MS Exchange Address Book File, Outlook Personal Folder File (Microsoft)


Python script


Python script


Python script


Python script


Python script


Python script



Registration Information/Key for W95/98, Registry Data File


Windows Explorer Command


Windows Screen Saver


Windows Script Component, Foxpro Screen (Microsoft)


Windows Shortcut into a Document


Shell Scrap Object File



Desktop theme file settings


Temporary File/Folder


Internet Location


VBScript File or Any Visual Basic Source


VBScript Encoded Script File


Visual Basic project file


VBScript Script File, Visual Basic for Applications Script


Virtual Hard Disk


Virtual Hard Disk Extended


Visual Studio .NET Binary-based Macro Project (Microsoft)


Visio Workspace File (Microsoft)


Internet printing file


Pinned site shortcut from Internet Explorer





Windows Script File


Windows Script Component


Windows Script File


Windows Script Host Settings File


Browser applications


Excel add-in


Exchange Public Folder Shortcut

You are evaluating Refined.