Defender for Office365 is an extra layer of security for Office 365.
For more info please see our article: What is Microsoft Defender for Office 365?
Please follow our guide: How to release a message from quarantine to resolve the issue.
There are many reasons why an email could be quarantined or blocked.
Unsafe attachments, suspected spam, suspected phishing, and suspected impersonation are just a few items on a very long list that could cause an email to be flagged.
How to release a message from quarantine
If you believe a message has been blocked, please contact Sentrian or your designated Quarantine Admin.
This means even though your message has been delivered, but the attachment is still being scanned. If it is a Microsoft Office document or PDF you should be able to preview it, otherwise please wait for the scan to complete.
Learn more about Safe Attachments: What are Safe Attachments?
This means you have unactioned messages sitting in your quarantine.
Please follow our article: How to release a message from quarantine
No. In fact, no advanced threat protection product can catch 100% of malicious attacks. This is why the best protection is still YOU!
How to check if a suspicious email is safe
It will not expire or time out
To protect against mass email campaigns and prevent you from being spammed by Microsofts system you will only receive one email per day.
This is why Sentrian recommends you check your quarantine regularly.
Only emails flagged as spam are accessible in the user quarantine, emails flagged as malicious or phishing are not accessible to the user.
If you believe an email has been flagged as malicious or phishing, please contact Sentrian or your designated Quarantine Admin.
The security landscape is ever-changing, and as fast as threats are blocked many more are created.
This is why Defender for Office 365 includes a great feature called Zero-hour auto purge (ZAP), this enables emails to retroactively be removed after they have reached your inbox if they are discovered to be malicious
Read more about ZAP: here