As you know, with Office 365 and Exchange Online, emails potentially identified as spam but not 100% identified as is are put in a quarantine.

End-users can release these mails and set it as false positive as well as the Exchange Online administrators.

A recent update on Exchange Online has introduced a new (and very helpful) feature for Exchange Online administrators (this is not (yet?) available for end-users): administrators can now previsualize the content of the quarantine mail before deciding to release or not on behalf of the end-user.

When you access the Exchange Control Panel and go to the Protection section and then the Quarantine tab, click on the Preview email message link