I found a good reference located at https://docs.microsoft.com/en-us/ex...-send-email-using-microsoft-365-or-office-365 I've been using "option 2" for a while now ...

I did this once a long, long time ago. They want to have an Assistant have a nickname so they can send to whichever name the owners want, but they want it to appear in the mailbox as if it was sent to ...