Information on blocked email attachments

The person you sent the email to won’t have received it or know that you tried to send them a message.

In addition, if someone external to the University is sending you an email containing a high risk attachment this will also be blocked, and they will receive a failure notification.

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The University of Oxford blocks emails containing attachments with file extensions that are commonly used in email malware campaigns.

You must make sure that you don’t share personal or sensitive data insecurely, for example by email. See the University's Information Security website for the latest advice and guidance on keeping data secure.

If you are external to the University of Oxford please get in contact with the file recipient to discuss your options. The recipient can, for example, set up a folder for you on the University’s file sharing service, OxFile, where you can upload your file.



Files in your OneDrive for Business cloud storage can be shared with internal and external recipients very easily and securely.


OxFile provides a simple way to share files of up to 25GB in size. You can share files internally and externally. People external to the University can also use OxFile to share files with you; you will need to set up a folder for them to do this.


Your personal SharePoint area, MySite/One Drive, allows you to share files with other members of the University securely.  To upload a blocked file type you will need to upload it as a ZIP file. See information about creating a ZIP file below.

If you need help getting started with or using SharePoint contact your local SharePoint Co-ordinator.

ZIP files

You can email the blocked file types if you save and email them as a ZIP file. We recommend that ZIP files are password protected.

See information about how to create a ZIP file below.

External File Sharing Services

See the University's Information Security website for the latest advice and guidance on using external services.


If you are sending public or non-sensitive information then you can use the built-in Windows ZIP tool:

  1. Press Start  + E to open Windows Explorer, and locate the file you want to send
  2. Right click on the file, choose Send To > Compressed (zipped) folder
  3. The ZIP file will be created in the same folder as your original file

For sending files containing personal data or any other sensitive information, we recommend using 7zip to create an encrypted ZIP file:

  1. Download and install 7zip if it is not already available on your PC
  2. Right click the file name and select 7-Zip and Add to archive…
  3. When prompted enter a filename for the ZIP file
  4. Select zip from the Archive format drop down list
  5. Enter a password (Information Security guidance is to use 16 characters or more)
  6. Select ZipCrypto as the Encryption method (AES-256 offers greater theoretical security, but ZipCrypto is more widely supported)
  7. Click OK
  8. Again, the ZIP file will be created in the same folder as your original file

Please contact the person you would like to send the file to for help.

Contact your local IT Support Staff or the Service Desk at IT Services.

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