Django not sending emails to admins

Question

According to the documentation, if DEBUG is set to False and something is provided under the ADMINS setting, Django will send an email

Answer 1

In my case, it's the include_html in mail_admins.

When I set include_html to True,the email server reject to send my email because it think that my emails are spam.

Everything works just fine when I set include_html to False.