Instead of having default sender as email@example.com, Tenant SharePoint app should have facility to use specific sender address
In hybrid environment lots of customization always in demand. One of the case is having specific sender email address for mass communication via Shrepoint Online app to the respective Tenants users hosted in onPrem AD environment.
Therefore, its good to have app level custom setting to achieve the above
Ian Crew commented
Hopefully the UserVoice admins can consolidate these ideas, and their votes, into a single one.