perenecabuto/django-sendmail-backend — pull request #5 by name-no (2014-12-08 06:37:50+00:00)
Title: add support for Bcc

Django splits out the 'Bcc:' header from a message, and that is why sender have to list recipients explicitly in the sendmail commandline args.

Here is a supportive link: https://code.djangoproject.com/ticket/18582