Universiteit Leiden

nl en


You receive an email 'in quarantine': what does that mean?

10 January 2023

An email from Microsoft with the message that an email addressed to you has been placed in quarantine. You may have received this recently if your Outlook has been migrated to the online Exchange environment. What does this mean? We give you a brief explanation. 

Is an email in quarantine safe?

The security requirements for all incoming emails to the university have recently become more strict. If an email does not meet the requirements, it may be intercepted by the spam filter or by Microsoft's quarantine service. Unfortunately, not only real spam or phishing messages are stopped, but in some cases valid emails are intercepted as well. 

Do you get a notification from Microsoft about a message in quarantine? This is an automated, and safe, Microsoft service. The sender of the message will be: quarantine@messaging.microsoft.com. It refers to an email that may contain spam or that may be dangerous (see phishing mail). The suspect mail has been placed in a secure environment so that you can view the content without any risk. The notification from Microsoft will be repeated every three days. After 30 days in quarantine, a suspect message will be permanently deleted. 

What should I do with an email in quarantine? 

You can view the message from Microsoft safely. It will contain the following information:  

  • Sender: the name of the sender and the email address of the message that has been placed in quarantine   
  • Subject: the subject line of the message that has been placed in quarantine
  • Date: the date and time (in UTC) when the messaage was placed in quarantine

You can then take the following actions: 

  • Block the sender: add the sender of the email to the list of blocked senders in your mailbox.  
  • Release: if it is a spam mail, you can release the mail straight away, or delete it. (This option is not available for a phishing mail). 
  • Check: you can use the “check” link to check the message safely. In the browser you go directly to the Security and Compliance centre, where you can view your quarantined message. You can then release it, delete or report it. 

How to prevent the emails you send from being intercepted?

  1. Do not send university emails from external servers. If, for example, you send a newsletter using an external email programme, or automated emails from a website that is hosted externally, then the spam filters will mark these emails as spam.
  2. Do you wish to have an exception made for the external mail server or service that you are using? Then please contact the helpdesk. Do you wish to send a bulk email? Contact the helpdesk to find out what your options are.

Read more

This website uses cookies.  More information.