==============
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)

Mail will be sent using the SMTP host and port specified in the `EMAIL_HOST`_
and `EMAIL_PORT`_ settings. The `EMAIL_HOST_USER`_ and `EMAIL_HOST_PASSWORD`_
settings, if set, will be used to authenticate to the SMTP server and the
`EMAIL_USE_TLS`_ settings will control whether a secure connection is used.

.. note::

    The character set of email sent with ``django.core.mail`` will be set to
    the value of your `DEFAULT_CHARSET setting`_.

.. _DEFAULT_CHARSET setting: ../settings/#default-charset
.. _EMAIL_HOST: ../settings/#email-host
.. _EMAIL_PORT: ../settings/#email-port
.. _EMAIL_HOST_USER: ../settings/#email-host-user
.. _EMAIL_HOST_PASSWORD: ../settings/#email-host-password
.. _EMAIL_USE_TLS: ../settings/#email-use-tls


send_mail()
===========

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, auth_user=None,
        auth_password=None)

The ``subject``, ``message``, ``from_email`` and ``recipient_list`` parameters
are required.

    * ``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``.
    * ``auth_user``: The optional username to use to authenticate to the SMTP
      server. If this isn't provided, Django will use the value of the
      ``EMAIL_HOST_USER`` setting.
    * ``auth_password``: The optional password to use to authenticate to the
      SMTP server. If this isn't provided, Django will use the value of the
      ``EMAIL_HOST_PASSWORD`` setting.

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

send_mass_mail()
================

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

    send_mass_mail(datatuple, fail_silently=False,
        auth_user=None, auth_password=None):

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

    (subject, message, from_email, recipient_list)

``fail_silently``, ``auth_user`` and ``auth_password`` have the same functions
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 all of its messages.
This makes ``send_mass_mail()`` slightly more efficient.

mail_admins()
=============

``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`_.

This method exists for convenience and readability.

.. _ADMINS setting: ../settings/#admins
.. _EMAIL_SUBJECT_PREFIX setting: ../settings/#email-subject-prefix
.. _SERVER_EMAIL setting: ../settings/#server-email

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: ../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

The EmailMessage and SMTPConnection classes
===========================================

Django's `send_mail()` and `send_mass_mail()` functions are actually thin
wrappers that make use of the `EmailMessage` and `SMTPConnection` classes in
`django.mail`.  If you ever need to customize the way Django sends email, you
can subclass these two classes to suit your needs.

.. note::
    Not all features of the `EmailMessage` class are available through the
    `send_mail()` and related wrapper functions. If you wish to use advanced
    features such as including BCC recipients or multi-part email, you will
    need to create `EmailMessage` instances directly.

In general, `EmailMessage` is responsible for creating the email message
itself. `SMTPConnection` is responsible for the network connection side of the
operation. This means you can reuse the same connection (an `SMTPConnection`
instance) for multiple messages.

The `EmailMessage` class has the following methods that you can use:

 * `send()` sends the message, using either the connection that is specified
   in the `connection` attribute, or creating a new connection if none already
   exists.
 * `message()` constructs a `django.core.mail.SafeMIMEText` object (a
   sub-class of Python's `email.MIMEText.MIMEText` class) holding the message
   to be sent. If you ever need to extend the `EmailMessage` class, you will
   probably want to override this method to put the content you wish into the
   MIME object.

The `SMTPConnection` class is initialized with the host, port, username and
password for the SMTP server. If you don't specify one or more of those
options, they are read from your settings file.

If you are sending lots of messages at once, the `send_messages()` method of
the `SMTPConnection` class will be useful. It takes a list of `EmailMessage`
instances (or sub-classes) and sends them over a single connection. For
example, if you have a function called `get_notification_email()` that returns a
list of `EmailMessage` objects representing some periodic email you wish to
send out, you could send this with::

    connection = SMTPConnection()   # Use default settings for connection
    messages = get_notification_email()
    connection.send_messages(messages)