email.txt

.. _topics-email:

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

.. module:: django.core.mail
   :synopsis: Helpers to easily send 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://docs.python.org/library/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 is sent using the SMTP host and port specified in the :setting:`EMAIL_HOST`
and :setting:`EMAIL_PORT` settings. The :setting:`EMAIL_HOST_USER` and
:setting:`EMAIL_HOST_PASSWORD` settings, if set, are used to authenticate to the
SMTP server, and the :setting:`EMAIL_USE_TLS` setting controls whether a secure
connection is used.

.. note::

    The character set of e-mail sent with ``django.core.mail`` will be set to
    the value of your :setting:`DEFAULT_CHARSET` setting.

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

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

    .. function:: 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://docs.python.org/library/smtplib.html

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

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

    .. function:: 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' "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 :setting:`ADMINS` setting. Here's the definition:

    .. function:: mail_admins(subject, message, fail_silently=False)

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

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

This method exists for convenience and readability.

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 :setting:`MANAGERS`
setting. Here's the definition:

    .. function:: mail_managers(subject, message, fail_silently=False)

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 form class
            # to get proper validation errors.
            return HttpResponse('Make sure all fields are entered and valid.')

.. _Header injection: http://www.nyphp.org/phundamentals/email_header_injection.php

.. _emailmessage-and-smtpconnection:

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

.. versionadded:: 1.0

Django's ``send_mail()`` and ``send_mass_mail()`` functions are actually thin
wrappers that make use of the ``EmailMessage`` and ``SMTPConnection`` classes
in ``django.core.mail``.  If you ever need to customize the way Django sends
e-mail, 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 BCC'ed recipients, file attachments, or multi-part
    e-mail, you'll need to create ``EmailMessage`` instances directly.

    This is a design feature. ``send_mail()`` and related functions were
    originally the only interface Django provided. However, the list of
    parameters they accepted was slowly growing over time. It made sense to
    move to a more object-oriented design for e-mail messages and retain the
    original functions only for backwards compatibility.

In general, ``EmailMessage`` is responsible for creating the e-mail 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.

EmailMessage Objects
--------------------

.. class:: EmailMessage

The ``EmailMessage`` class is initialized with the following parameters (in
the given order, if positional arguments are used). All parameters are
optional and can be set at any time prior to calling the ``send()`` method.

    * ``subject``: The subject line of the e-mail.

    * ``body``: The body text. This should be a plain text message.

    * ``from_email``: The sender's address. Both ``fred@example.com`` and
      ``Fred <fred@example.com>`` forms are legal. If omitted, the
      :setting:`DEFAULT_FROM_EMAIL` setting is used.

    * ``to``: A list or tuple of recipient addresses.

    * ``bcc``: A list or tuple of addresses used in the "Bcc" header when
      sending the e-mail.

    * ``connection``: An ``SMTPConnection`` instance. Use this parameter if
      you want to use the same connection for multiple messages. If omitted, a
      new connection is created when ``send()`` is called.

    * ``attachments``: A list of attachments to put on the message. These can
      be either ``email.MIMEBase.MIMEBase`` instances, or ``(filename,
      content, mimetype)`` triples.

    * ``headers``: A dictionary of extra headers to put on the message. The
      keys are the header name, values are the header values. It's up to the
      caller to ensure header names and values are in the correct format for
      an e-mail message.

For example::

    email = EmailMessage('Hello', 'Body goes here', 'from@example.com',
                ['to1@example.com', 'to2@example.com'], ['bcc@example.com'],
                headers = {'Reply-To': 'another@example.com'})

The class has the following methods:

    * ``send(fail_silently=False)`` sends the message, using either
      the connection that is specified in the ``connection``
      attribute, or creating a new connection if none already
      exists. If the keyword argument ``fail_silently`` is ``True``,
      exceptions raised while sending the message will be quashed.

    * ``message()`` constructs a ``django.core.mail.SafeMIMEText`` object (a
      subclass of Python's ``email.MIMEText.MIMEText`` class) or a
      ``django.core.mail.SafeMIMEMultipart`` object holding the
      message to be sent. If you ever need to extend the ``EmailMessage`` class,
      you'll probably want to override this method to put the content you want
      into the MIME object.

    * ``recipients()`` returns a list of all the recipients of the message,
      whether they're recorded in the ``to`` or ``bcc`` attributes. This is
      another method you might need to override when subclassing, because the
      SMTP server needs to be told the full list of recipients when the message
      is sent. If you add another way to specify recipients in your class, they
      need to be returned from this method as well.

    * ``attach()`` creates a new file attachment and adds it to the message.
      There are two ways to call ``attach()``:

       * You can pass it a single argument that is an
         ``email.MIMEBase.MIMEBase`` instance. This will be inserted directly
         into the resulting message.

       * Alternatively, you can pass ``attach()`` three arguments:
         ``filename``, ``content`` and ``mimetype``. ``filename`` is the name
         of the file attachment as it will appear in the e-mail, ``content`` is
         the data that will be contained inside the attachment and
         ``mimetype`` is the optional MIME type for the attachment. If you
         omit ``mimetype``, the MIME content type will be guessed from the
         filename of the attachment.

         For example::

            message.attach('design.png', img_data, 'image/png')

    * ``attach_file()`` creates a new attachment using a file from your
      filesystem. Call it with the path of the file to attach and, optionally,
      the MIME type to use for the attachment. If the MIME type is omitted, it
      will be guessed from the filename. The simplest use would be::

        message.attach_file('/images/weather_map.png')

.. _DEFAULT_FROM_EMAIL: ../settings/#default-from-email

Sending alternative content types
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It can be useful to include multiple versions of the content in an e-mail;
the classic example is to send both text and HTML versions of a message. With
Django's e-mail library, you can do this using the ``EmailMultiAlternatives``
class. This subclass of ``EmailMessage`` has an ``attach_alternative()`` method
for including extra versions of the message body in the e-mail. All the other
methods (including the class initialization) are inherited directly from
``EmailMessage``.

To send a text and HTML combination, you could write::

    from django.core.mail import EmailMultiAlternatives

    subject, from_email, to = 'hello', 'from@example.com', 'to@example.com'
    text_content = 'This is an important message.'
    html_content = '<p>This is an <strong>important</strong> message.</p>'
    msg = EmailMultiAlternatives(subject, text_content, from_email, [to])
    msg.attach_alternative(html_content, "text/html")
    msg.send()

By default, the MIME type of the ``body`` parameter in an ``EmailMessage`` is
``"text/plain"``. It is good practice to leave this alone, because it
guarantees that any recipient will be able to read the e-mail, regardless of
their mail client. However, if you are confident that your recipients can
handle an alternative content type, you can use the ``content_subtype``
attribute on the ``EmailMessage`` class to change the main content type. The
major type will always be ``"text"``, but you can change it to the subtype. For
example::

    msg = EmailMessage(subject, html_content, from_email, [to])
    msg.content_subtype = "html"  # Main content is now text/html
    msg.send()

SMTPConnection Objects
----------------------

.. class:: SMTPConnection

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're sending lots of messages at once, the ``send_messages()`` method of
the ``SMTPConnection`` class is useful. It takes a list of ``EmailMessage``
instances (or subclasses) 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 e-mail 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)

Testing e-mail sending
----------------------

The are times when you do not want Django to send e-mails at all. For example,
while developing a website, you probably don't want to send out thousands of
e-mails -- but you may want to validate that e-mails will be sent to the right
people under the right conditions, and that those e-mails will contain the
correct content.

The easiest way to test your project's use of e-mail is to use a "dumb" e-mail
server that receives the e-mails locally and displays them to the terminal,
but does not actually send anything. Python has a built-in way to accomplish
this with a single command::

    python -m smtpd -n -c DebuggingServer localhost:1025

This command will start a simple SMTP server listening on port 1025 of
localhost. This server simply prints to standard output all email headers and
the email body. You then only need to set the :setting:`EMAIL_HOST` and
:setting:`EMAIL_PORT` accordingly, and you are set.

For more entailed testing and processing of e-mails locally, see the Python
documentation on the `SMTP Server`_.

.. _SMTP Server: http://docs.python.org/library/smtpd.html