Outlook stops some file types because attachments spread viruses. Affected files include .exe, .bat, .cmd, .js, .vbs, .msi and .lnk. Microsoft names three workarounds. Share the file through OneDrive or SharePoint, compress it into a ZIP file or rename the extension. Exchange administrators can unblock file types on the server.
You send or open an attachment and Outlook refuses it. Microsoft explains one reason for this on its Support site and gives workarounds for senders and recipients.
Facts follow the Microsoft Support page on blocked attachments in Outlook. Network drops and server timeouts are not described there. That page explains file types that Outlook stops on purpose.
Why does Outlook Block Attachments?
Attachments are a common way to spread computer viruses. Outlook stops sending and receiving of certain file types to protect you and your recipients. Examples from the Microsoft list include .exe, .bat, .cmd, .js, .vbs, .ps1, .msi, .msp, .lnk, .url, .reg and .mdb files.
Microsoft does not quote the message text on that page and does not say how the list is updated.
How to Send a Restricted File?
- Share a link. Upload the file to OneDrive or SharePoint and send the link. Recipients download the file from the link.
- Compress the file. ZIP archives use an extension that Outlook accepts. Windows creates a zipped folder from the Send to menu.
- Rename the extension. Switch .exe to .docx for example. Recipients save the file and rename it back before use. Microsoft calls this a workaround.
Open files only from senders you trust. Renaming does not remove the risk inside the file.
What can an Administrator do?
- Exchange accounts. Email server administrators can unblock certain file types or adjust mailbox security settings.
- Other accounts. Microsoft describes an advanced registry procedure in Microsoft Support article KB 829982. That Outlook page names no registry key.
What if the File Type is Allowed?
Microsoft gives no steps for connection drops or timeouts on that page. See why Outlook cannot open an attachment for the temporary file folder error and how to delete an attachment from an Outlook email for removing a file you no longer need.
Frequently Asked Questions
Why does Outlook Block an Attachment?
Microsoft states attachments are a common way to spread computer viruses. Outlook stops certain file types to protect you.
Which File Types does Outlook Block?
Microsoft lists executables and scripts including .exe, .bat, .cmd, .js and .vbs. Installers like .msi and .msp and shortcut files like .lnk and .url are on the list too.
Can I Send a Blocked File?
Yes. Share a OneDrive or SharePoint link or compress the file into a ZIP archive.
Who can Unblock File Types?
Exchange administrators can unblock certain file types on the server.
Key Takeaways
- Outlook stops risky file types to prevent viruses.
- OneDrive links and ZIP files get past the filter.
- Renaming the extension is a workaround and needs a rename back.
- Exchange administrators can unblock file types.
- That Microsoft page explains file types and not network drops.
Sources and References
Facts follow Microsoft Support.
- Blocked attachments in Outlook (Microsoft Support) support.microsoft.com