==============
Sending e-mail
==============

Although Python makes sending e-mail relatively easy via the `smtplib library`_,
Django provides a couple of light wrappers over it, to make sending e-mail
extra quick.

The code lives in a single module: ``django.core.mail``.

.. _smtplib library: http://www.python.org/doc/current/lib/module-smtplib.html

Quick example
=============

In two lines::

    from django.core.mail import send_mail

    send_mail('Subject here', 'Here is the message.', 'from@example.com',
        ['to@example.com'], fail_silently=False)

The send_mail function
======================

The simplest way to send e-mail is using the function
``django.core.mail.send_mail``. Here's its definition::

    send_mail(subject, message, from_email, recipient_list, fail_silently=False)

All parameters are required except for ``fail_silently``, which is ``False`` by
default.

    * ``subject``: A string.
    * ``message``: A string.
    * ``from_email``: A string.
    * ``recipient_list``: A list of strings, each an e-mail address. Each
      member of ``recipient_list`` will see the other recipients in the "To:"
      field of the e-mail message.
    * ``fail_silently``: A boolean. If it's ``False``, ``send_mail`` will raise
      an ``smtplib.SMTPException``. See the `smtplib docs`_ for a list of
      possible exceptions, all of which are subclasses of ``SMTPException``.

.. _smtplib docs: http://www.python.org/doc/current/lib/module-smtplib.html

The send_mass_mail function
===========================

``django.core.mail.send_mass_mail`` is intended to handle mass e-mailing.
Here's the definition::

    send_mass_mail(datatuple, fail_silently=False):

``datatuple`` is a tuple in which each element is in this format::

    (subject, message, from_email, recipient_list)

``fail_silently`` has the same function as in ``send_mail()``.

Each separate element of ``datatuple`` results in a separate e-mail message.
As in ``send_mail()``, recipients in the same ``recipient_list`` will all see
the other addresses in the e-mail messages's "To:" field.

send_mass_mail vs. send_mail
----------------------------

The main difference between ``send_mass_mail()`` and ``send_mail()`` is that
``send_mail()`` opens a connection to the mail server each time it's executed,
while ``send_mass_mail()`` uses a single connection for each of its messages.
This makes ``send_mass_mail()`` slightly more efficient.

The mail_admins function
========================

``django.core.mail.mail_admins`` is a shortcut for sending an e-mail to the
site admins, as defined in the `ADMINS setting`_. Here's the definition::

    mail_admins(subject, message, fail_silently=False)

``mail_admins()`` prefixes the subject with the value of the
`EMAIL_SUBJECT_PREFIX setting`_, which is ``"[Django] "`` by default.

The "From:" header of the e-mail will be the value of the `SERVER_EMAIL setting`_.

.. _ADMINS setting: http://www.djangoproject.com/documentation/settings/#admins
.. _EMAIL_SUBJECT_PREFIX setting: http://www.djangoproject.com/documentation/settings/#email-subject-prefix
.. _SERVER_EMAIL setting: http://www.djangoproject.com/documentation/settings/#server-email

The mail_managers function
==========================

``django.core.mail.mail_managers`` is just like ``mail_admins``, except it
sends an e-mail to the site managers, as defined in the `MANAGERS setting`_.
Here's the definition::

    mail_managers(subject, message, fail_silently=False)

.. _MANAGERS setting: http://www.djangoproject.com/documentation/settings/#managers

Examples
========

This sends a single e-mail to john@example.com and jane@example.com, with them
both appearing in the "To:"::

    send_mail('Subject', 'Message.', 'from@example.com',
        ['john@example.com', 'jane@example.com'])

This sends a message to john@example.com and jane@example.com, with them both
receiving a separate e-mail::

    datatuple = (
        ('Subject', 'Message.', 'from@example.com', ['john@example.com'],
        ('Subject', 'Message.', 'from@example.com', ['jane@example.com'],
    )
    send_mass_mail(datatuple)

Preventing header injection
===========================

`Header injection`_ is a security exploit in which an attacker inserts extra
e-mail headers to control the "To:" and "From:" in e-mail messages that your
scripts generate.

The Django e-mail functions outlined above all protect against header injection
by forbidding newlines in header values. If any ``subject``, ``from_email`` or
``recipient_list`` contains a newline (in either Unix, Windows or Mac style),
the e-mail function (e.g. ``send_mail()``) will raise
``django.core.mail.BadHeaderError`` (a subclass of ``ValueError``) and, hence,
will not send the e-mail. It's your responsibility to validate all data before
passing it to the e-mail functions.

If a ``message`` contains headers at the start of the string, the headers will
simply be printed as the first bit of the e-mail message.

Here's an example view that takes a ``subject``, ``message`` and ``from_email``
from the request's POST data, sends that to admin@example.com and redirects to
"/contact/thanks/" when it's done::

    from django.core.mail import send_mail, BadHeaderError

    def send_email(request):
        subject = request.POST.get('subject', '')
        message = request.POST.get('message', '')
        from_email = request.POST.get('from_email', '')
        if subject and message and from_email:
            try:
                send_mail(subject, message, from_email, ['admin@example.com'])
            except BadHeaderError:
                return HttpResponse('Invalid header found.')
            return HttpResponseRedirect('/contact/thanks/')
        else:
            # In reality we'd use a manipulator
            # to get proper validation errors.
            return HttpResponse('Make sure all fields are entered and valid.')

.. _Header injection: http://securephp.damonkohler.com/index.php/Email_Injection
