Django2.0手册:Sending email



Although Python makes sending email relatively easy via the smtplib
module, Django provides a couple of light wrappers over it. These wrappers are
provided to make sending email extra quick, to make it easy to test email
sending during development, and to provide support for platforms that can’t use
SMTP.

The code lives in the django.core.mail module.

快速上手¶

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
EMAIL_HOST and EMAIL_PORT settings. The
EMAIL_HOST_USER and EMAIL_HOST_PASSWORD settings, if
set, are used to authenticate to the SMTP server, and the
EMAIL_USE_TLS and EMAIL_USE_SSL settings 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.

send_mail()¶

send_mail(subject, message, from_email, recipient_list, fail_silently=False, auth_user=None, auth_password=None, connection=None, html_message=None)[source]

The simplest way to send email is using
django.core.mail.send_mail().

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 email address. Each
    member of recipient_list will see the other recipients in the “To:”
    field of the email 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.
  • connection: The optional email backend to use to send the mail.
    If unspecified, an instance of the default backend will be used.
    See the documentation on Email backends
    for more details.
  • html_message: If html_message is provided, the resulting email will be a
    multipart/alternative email with message as the
    text/plain content type and html_message as the
    text/html content type.

The return value will be the number of successfully delivered messages (which
can be 0 or 1 since it can only send one message).

send_mass_mail()¶

send_mass_mail(datatuple, fail_silently=False, auth_user=None, auth_password=None, connection=None)[source]

django.core.mail.send_mass_mail() is intended to handle mass emailing.

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 email message.
As in send_mail(), recipients in the same
recipient_list will all see the other addresses in the email messages’
“To:” field.

For example, the following code would send two different messages to
two different sets of recipients; however, only one connection to the
mail server would be opened:

message1 = ('Subject here', 'Here is the message', 'from@example.com', ['first@example.com', 'other@example.com'])
message2 = ('Another Subject', 'Here is another message', 'from@example.com', ['second@test.com'])
send_mass_mail((message1, message2), fail_silently=False)

The return value will be the number of successfully delivered messages.

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()¶

mail_admins(subject, message, fail_silently=False, connection=None, html_message=None)[source]

django.core.mail.mail_admins() is a shortcut for sending an email to the
site admins, as defined in the ADMINS setting.

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

The “From:” header of the email will be the value of the
SERVER_EMAIL setting.

This method exists for convenience and readability.

If html_message is provided, the resulting email will be a
multipart/alternative email with message as the
text/plain content type and html_message as the
text/html content type.

mail_managers()¶

mail_managers(subject, message, fail_silently=False, connection=None, html_message=None)[source]

django.core.mail.mail_managers() is just like mail_admins(), except it
sends an email to the site managers, as defined in the MANAGERS
setting.

示例¶

This sends a single email 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 email:

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
email headers to control the “To:” and “From:” in email messages that your
scripts generate.

The Django email 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 email function (e.g. send_mail()) will raise
django.core.mail.BadHeaderError (a subclass of ValueError) and, hence,
will not send the email. It’s your responsibility to validate all data before
passing it to the email functions.

If a message contains headers at the start of the string, the headers will
simply be printed as the first bit of the email 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 BadHeaderError, send_mail
from django.http import HttpResponse, HttpResponseRedirect

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.')

The EmailMessage class¶

Django’s send_mail() and
send_mass_mail() functions are actually thin
wrappers that make use of the EmailMessage class.

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 email, you’ll need to create
EmailMessage instances directly.

Note

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 email
messages and retain the original functions only for backwards
compatibility.

EmailMessage is responsible for creating the email
message itself. The email backend is then
responsible for sending the email.

For convenience, EmailMessage provides a simple
send() method for sending a single email. If you need to send multiple
messages, the email backend API provides an alternative.

EmailMessage Objects¶

class EmailMessage[source]

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 email.
  • 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
    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 email.
  • connection: An email backend 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 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 email message. The corresponding attribute is extra_headers.
  • cc: A list or tuple of recipient addresses used in the “Cc” header
    when sending the email.
  • reply_to: A list or tuple of recipient addresses used in the “Reply-To”
    header when sending the email.

例如:

from django.core.mail import EmailMessage

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

The class has the following methods:

  • send(fail_silently=False) sends the message. If a connection was
    specified when the email was constructed, that connection will be used.
    Otherwise, an instance of the default backend will be instantiated and
    used. If the keyword argument fail_silently is True, exceptions
    raised while sending the message will be quashed. An empty list of
    recipients will not raise an exception.

  • message() constructs a django.core.mail.SafeMIMEText object (a
    subclass of Python’s 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, cc 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 a
      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 email, 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.

      例如:

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

      If you specify a mimetype of message/rfc822, it will also accept
      django.core.mail.EmailMessage and email.message.Message.

      For a mimetype starting with text/, content is expected to be a
      string. Binary data will be decoded using UTF-8, and if that fails, the
      MIME type will be changed to application/octet-stream and the data will
      be attached unchanged.

      In addition, message/rfc822 attachments will no longer be
      base64-encoded in violation of RFC 2046#section-5.2.1, which can cause
      issues with displaying the attachments in Evolution and Thunderbird.

  • 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')
    

    For MIME types starting with text/, binary data is handled as in
    attach().

Changed in Django 1.11:

Added the fallback to MIME type application/octet-stream when binary
data for a text/* attachment cannot be decoded.

Sending alternative content types

It can be useful to include multiple versions of the content in an email; the
classic example is to send both text and HTML versions of a message. With
Django’s email 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 email. 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 email, 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 the
subtype. For example:

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

Email backends¶

The actual sending of an email is handled by the email backend.

The email backend class has the following methods:

  • open() instantiates a long-lived email-sending connection.
  • close() closes the current email-sending connection.
  • send_messages(email_messages) sends a list of
    EmailMessage objects. If the connection is
    not open, this call will implicitly open the connection, and close the
    connection afterwards. If the connection is already open, it will be
    left open after mail has been sent.

It can also be used as a context manager, which will automatically call
open() and close() as needed:

from django.core import mail

with mail.get_connection() as connection:
    mail.EmailMessage(
        subject1, body1, from1, [to1],
        connection=connection,
    ).send()
    mail.EmailMessage(
        subject2, body2, from2, [to2],
        connection=connection,
    ).send()

Obtaining an instance of an email backend¶

The get_connection() function in django.core.mail returns an
instance of the email backend that you can use.

get_connection(backend=None, fail_silently=False, *args, **kwargs)[source]

By default, a call to get_connection() will return an instance of the
email backend specified in EMAIL_BACKEND. If you specify the
backend argument, an instance of that backend will be instantiated.

The fail_silently argument controls how the backend should handle errors.
If fail_silently is True, exceptions during the email sending process
will be silently ignored.

All other arguments are passed directly to the constructor of the
email backend.

Django ships with several email sending backends. With the exception of the
SMTP backend (which is the default), these backends are only useful during
testing and development. If you have special email sending requirements, you
can write your own email backend.

SMTP backend

class backends.smtp.EmailBackend(host=None, port=None, username=None, password=None, use_tls=None, fail_silently=False, use_ssl=None, timeout=None, ssl_keyfile=None, ssl_certfile=None, **kwargs)

This is the default backend. Email will be sent through a SMTP server.

The value for each argument is retrieved from the matching setting if the
argument is None:

The SMTP backend is the default configuration inherited by Django. If you
want to specify it explicitly, put the following in your settings:

EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'

If unspecified, the default timeout will be the one provided by
socket.getdefaulttimeout(), which defaults to None (no timeout).

Console backend

Instead of sending out real emails the console backend just writes the
emails that would be sent to the standard output. By default, the console
backend writes to stdout. You can use a different stream-like object by
providing the stream keyword argument when constructing the connection.

To specify this backend, put the following in your settings:

EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'

This backend is not intended for use in production — it is provided as a
convenience that can be used during development.

File backend

The file backend writes emails to a file. A new file is created for each new
session that is opened on this backend. The directory to which the files are
written is either taken from the EMAIL_FILE_PATH setting or from
the file_path keyword when creating a connection with
get_connection().

To specify this backend, put the following in your settings:

EMAIL_BACKEND = 'django.core.mail.backends.filebased.EmailBackend'
EMAIL_FILE_PATH = '/tmp/app-messages' # change this to a proper location

This backend is not intended for use in production — it is provided as a
convenience that can be used during development.

In-memory backend

The 'locmem' backend stores messages in a special attribute of the
django.core.mail module. The outbox attribute is created when the
first message is sent. It’s a list with an
EmailMessage instance for each message that would
be sent.

To specify this backend, put the following in your settings:

EMAIL_BACKEND = 'django.core.mail.backends.locmem.EmailBackend'

This backend is not intended for use in production — it is provided as a
convenience that can be used during development and testing.

Dummy backend

As the name suggests the dummy backend does nothing with your messages. To
specify this backend, put the following in your settings:

EMAIL_BACKEND = 'django.core.mail.backends.dummy.EmailBackend'

This backend is not intended for use in production — it is provided as a
convenience that can be used during development.

Defining a custom email backend¶

If you need to change how emails are sent you can write your own email
backend. The EMAIL_BACKEND setting in your settings file is then
the Python import path for your backend class.

Custom email backends should subclass BaseEmailBackend that is located in
the django.core.mail.backends.base module. A custom email backend must
implement the send_messages(email_messages) method. This method receives a
list of EmailMessage instances and returns the
number of successfully delivered messages. If your backend has any concept of
a persistent session or connection, you should also implement the open()
and close() methods. Refer to smtp.EmailBackend for a reference
implementation.

Sending multiple emails¶

Establishing and closing an SMTP connection (or any other network connection,
for that matter) is an expensive process. If you have a lot of emails to send,
it makes sense to reuse an SMTP connection, rather than creating and
destroying a connection every time you want to send an email.

There are two ways you tell an email backend to reuse a connection.

Firstly, you can use the send_messages() method. send_messages() takes
a list of EmailMessage instances (or subclasses),
and sends them all using 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 these emails using
a single call to send_messages:

from django.core import mail
connection = mail.get_connection()   # Use default email connection
messages = get_notification_email()
connection.send_messages(messages)

In this example, the call to send_messages() opens a connection on the
backend, sends the list of messages, and then closes the connection again.

The second approach is to use the open() and close() methods on the
email backend to manually control the connection. send_messages() will not
manually open or close the connection if it is already open, so if you
manually open the connection, you can control when it is closed. For example:

from django.core import mail
connection = mail.get_connection()

# Manually open the connection
connection.open()

# Construct an email message that uses the connection
email1 = mail.EmailMessage(
    'Hello',
    'Body goes here',
    'from@example.com',
    ['to1@example.com'],
    connection=connection,
)
email1.send() # Send the email

# Construct two more messages
email2 = mail.EmailMessage(
    'Hello',
    'Body goes here',
    'from@example.com',
    ['to2@example.com'],
)
email3 = mail.EmailMessage(
    'Hello',
    'Body goes here',
    'from@example.com',
    ['to3@example.com'],
)

# Send the two emails in a single call -
connection.send_messages([email2, email3])
# The connection was already open so send_messages() doesn't close it.
# We need to manually close the connection.
connection.close()

Configuring email for development¶

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

The easiest way to configure email for local development is to use the
console email backend. This backend
redirects all email to stdout, allowing you to inspect the content of mail.

The file email backend can also be useful
during development — this backend dumps the contents of every SMTP connection
to a file that can be inspected at your leisure.

Another approach is to use a “dumb” SMTP server that receives the emails
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 EMAIL_HOST and
EMAIL_PORT accordingly. For a more detailed discussion of SMTP
server options, see the Python documentation for the smtpd module.

For information about unit-testing the sending of emails in your application,
see the Email services section of the testing documentation.