Oct 15 2019 01:28 AM
Office 365 applications create lots of Azure Active Directory guest accounts. Here’s how to find old accounts and check their Office 365 group membership. If you know the accounts that are old and stale and aren’t members of any Office 365 group, you can consider removing them from your tenant.
https://office365itpros.com/2019/10/15/report-old-guest-accounts-office365-groups/