Hi @ Annette LaRosa ,
There are two ways you can allow messages from this sender:
1. On the Quarantine page in the Microsoft 365 Defender portal, select this sender's message, select Release email, and configure Add sender to your organization's allow list.
2. On the Quarantine page in the Microsoft 365 Defender portal, select this sender's message, select Submit only, and configure Select a reason for submitting to Microsoft, select Allow messages like this.
For additional information on managing quarantined messages, you can refer to this link: Manage quarantined messages and files as an admin - Office 365 | Microsoft Learn
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