Question is to Apple. Please fix it per subject.
1) Create a group in contacts (even as small as two names and two emails).
2) End Contacts.
3) End Mail.
4) Start Mail non-full screen, and start a new email.
5) Start Contacts and drag small group to Bcc: of new mail.
Mail Crashes with 'Mail quit unexpectedly.'
This is repeatable. I have sent the report to Apple.
I really need this to work for privacy and security of my mail list folks.