Drupal, Django, and WordPress are using localhost as SMTP server by default. But there is a way to use another SMTP server to send email.
- Django: Mail is sent using the SMTP host and port specified in the
EMAIL_HOST_PASSWORDsettings, if set, are used to authenticate to the SMTP server, and the
EMAIL_USE_SSLsettings control whether a secure connection is used. https://docs.djangoproject.com/en/1.10/topics/email/
- Drupal: install SMTP Authentication Support
- WordPress: WP Mail SMTP https://wordpress.org/plugins/wp-mail-smtp/