Mail on macOS Sonoma quits unexpectedly after opening the app
Created as it is not possible to post a reply in "Apple Mail quits unexpectedly after opening in Sonoma".
After identifying the culprit mail box using System Settings / Internet account, found a recent (of course) suspect mail that was indeed a spam message.
Removed it with the correspondant mail box Web mail, and that's it.
Now the issue is gone.
MacBook Pro 15″