How to Fix Microsoft 365 Blocking Email Attachments as Malware
Question details
The user needs to know how to safely receive or share email attachments that are being blocked by Microsoft 365 security filters due to suspected malware.
- Product
- Microsoft 365
- Device & OS
- not provided
- Scenario
- Attempting to send or receive an email attachment containing specific file types or suspected malware.
- Observed behavior
- Microsoft 365 removes or blocks the email attachment, preventing the recipient from accessing the file.
Never attempt to bypass malware protection by disabling security features. Always ensure you have an updated antivirus program running before handling suspicious files.
Use Secure File-Sharing Services Like OneDrive
Instead of attaching potentially flagged files directly to the email, use a cloud service to generate a secure sharing link.
Mail systems automatically block attachments suspected of containing malware. The sender’s system may be infected, or the attachment may contain an executable file or extension. Bypassing these filters is not recommended.
Ask the sender to run a local antivirus scan on the file to ensure it is genuinely safe and not infected.
Have the sender upload the scanned file to Microsoft OneDrive, Google Drive, or another approved secure file-sharing service.
Create a sharing link with appropriate access permissions so only the intended recipient can view or download the file.
Paste the sharing link into the email body and send the message instead of attaching the file directly.
Verify File Safety and Sender Intent
Ensure the file is not actually infected and that the sender intentionally sent it before attempting any workarounds.
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Frequently Asked Questions
Why does Microsoft 365 block my attachments even from trusted senders?
Microsoft 365 uses advanced security filters that scan all attachments for malware signatures and potentially dangerous file types (like .exe or .bat). These filters apply globally, so even trusted senders cannot bypass them if a file triggers a security rule.
Can I recover an attachment that Microsoft 365 removed for malware?
Typically, no. When Microsoft 365 removes an attachment for containing suspected malware, it quarantines or deletes the file to protect your system. You must ask the sender to share the file using a secure cloud link instead.
What file types are most commonly blocked by email security filters?
Executable files (.exe), batch scripts (.bat), installer packages (.msi), and macro-enabled documents (.docm, .xlsm) are frequently blocked by default because they are commonly used to distribute malware.
How can I safely send a false-positive file that keeps getting blocked?
The safest method is to upload the file to a cloud storage service like OneDrive or Google Drive and share the link via email. Alternatively, you can compress the file into a password-protected ZIP archive and provide the password to the recipient separately.
