The Exchange Online Protection service will send a spam summary message to your inbox on a periodic basis. If your account receives a large number of spam messages, these messages will arrive about once a week. If you don't receive as many, the notifications will arrive less frequently.
Release to Inbox sends the message to your Pitt Email (Outlook) inbox. If you report the message as Not Junk, then it will send a copy of the message to Microsoft for analysis so that spam filtering settings can be refined.
If you have not received an EOP ESN spam summary message recently and are concerned that an email you are expecting has been flagged, consider logging directly into Office 365 Quarantine web interface to check. This process is detailed here.