Exchange Online shared mailboxes only need licenses if they have an archive, exceed 50 GB in size, or are on litigation hold. The rules are there, but how many tenants check their shared mailboxes to make sure that they’re in compliance. This article explains how to use PowerShell to detect shared mailboxes that need licenses.
https://office365itpros.com/2022/08/17/shared-mailbox-license-check/
