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Blocking Emails with High Risk Attachments

If you have been directed to this page from a University of Oxford email delivery failure message your email has been blocked. 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.

Why was the email blocked?

The University of Oxford blocks emails with high risk file extensions, commonly used in email malware campaigns.  See a list of blocked file extensions (University of Oxford only).

File sharing options

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.

Non-University members

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.

University of Oxford members


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.  These should ideally be password protected.

External File Sharing Services

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

Further help

Non-University members

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

University members

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

Related information

Service area: 

Written by IT Services. Latest revision 30 November 2017