How to Update Shared Mailbox Owners About Quota Usage

An old script created to report quotas for user mailboxes provided the basis for email-based reporting of shared mailbox quotas. The old script used just Exchange Online PowerShell. This versions mixes Exchange Online and the Graph SDK and throws in some certificate-based authentication to boot to allow the script to send email from something other than the signed-in account.. It all comes together, using chunks of code from other scripts to speed up writing. It's the PowerShell way...