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* `_send_bulk` now allows each process to use multiple threads to send emails.
* Added support for mimetypes in email attachments. Thanks clickonchris!
* An `EmailTemplate` can now be used as defaults multiple times in one language. Thanks sac7e!
* `send_queued_mail` management command will now check whether there are more queued emails to be sent before exiting.
* Drop support for Django < 1.8. Thanks fendyh!