What are quarantined emails in Advanced Email Security?

Advanced Email Security scans your incoming messages for malware and phishing. Suspected messages are stored outside of your mailboxes, or quarantined, so they can be evaluated without putting your users at risk of malware or phishing. When a message is quarantined, it isn’t delivered to your Inbox or Junk folders.
How does Advanced Email Security decide to quarantine a message?
There are multiple levels of malware and phishing. When Advanced Email Security is confident that a message contains malware or phishing (like in the form of a link or attachment), the message is quarantined. Messages with other types of malware or phishing get routed to your Junk folder.
Where do messages get quarantined?
Advanced Email Security puts messages in the Microsoft 365 quarantine. From there, you can decide if the message should be released and delivered to the mailbox or deleted. By default, quarantined messages are only viewable by admins.
How do I know a message was quarantined?
With Advanced Email Security, users and admins will receive an email every 3 days notifying you of newly-quarantined messages. Users can't take any action on quarantined messages, but admins can review, release, and block the sender of them directly in the email.

How long does a message stayed quarantined?
Messages are quarantined for 15 days, and then the message expires. After a message expires in quarantine, it can’t be delivered to a mailbox.