EOP will send out notification of quarantined emails up to 3 times per day. If an email is quarantined, you will receive a notification email during the next notification cycle.
The notification cycle is controlled by a Microsoft automated process and the specific timing may vary slightly per user.
You can also log directly into the EOP Quarantine portal at any time to get a live look at what has been quarantined. Messages will show up in the quarantine list even if a notification has not been sent to you yet.