Enable in-domain email addresses for Alerts
Alerts on lists, libraries, pages, etc. can only be sent to Active Directory users recognized by SharePoint. Add an option to at least let emails within a specific domain (@mycompany.com) receive alerts. Or, allow a setting for any email address to get them if the tenant administrators deem it OK.
Right now we have email distribution lists whose membership can change, and we don't want to have to emulate those lists inside SharePoint groups just to be able to send alerts. Adding this functionality would solve that problem.