Emails quarantined by the Email Impersonation control or Email data protection is not visible in the recipient's quarantine portal but the email is visible to Quarantine administrator.
Email quarantined by Data protection policy or Impersonation control is not available in the quarantine portal.
The Data protection option is not enabled in the Email quarantine settings>Email Quarantine access and Notification Content.
The data protection option under "Users can view quarantined messages in Email Quarantine interface and summary notifications for the following services" in Services>Email quarantine must be enabled.
Please allow up to 1 hour for propagation and the User (non - admin) can view emails quarantined by data protection service.