Overview
As a user, you will receive an email digest giving a list of email messages quarantined as per rules configured on the Secure Mail flow system. (The frequency and schedule of the digest are controlled by your domain administrator.)
Using the links on the digest, you can release quarantine mail to your Inbox and also approve the sender such that the quarantined mail is released and the sender is added to your white-list.
Please refer to the document linked here to know the detailed steps.