Sending email

Although Python makes sending email relatively easy via the smtplibmodule, Django provides a couple of light wrappers over it. These wrappers areprovided to make sending email extra quick, to make it easy to test emailsending during development, and to provide support for platforms that can't useSMTP.

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

快速上手

In two lines:

  1. from django.core.mail import send_mail
  2.  
  3. send_mail(
  4.     'Subject here',
  5.     'Here is the message.',
  6.     'from@example.com',
  7.     ['to@example.com'],
  8.     fail_silently=False,
  9. )

Mail is sent using the SMTP host and port specified in theEMAIL_HOST and EMAIL_PORT settings. TheEMAIL_HOST_USER and EMAIL_HOST_PASSWORD settings, ifset, are used to authenticate to the SMTP server, and theEMAIL_USE_TLS and EMAIL_USE_SSL settings control whethera secure connection is used.

注解

The character set of email sent with django.core.mail will be set tothe value of your DEFAULT_CHARSET setting.

send_mail()

  • sendmail(_subject, message, from_email, recipient_list, fail_silently=False, auth_user=None, auth_password=None, connection=None, html_message=None)[源代码]
  • The simplest way to send email is usingdjango.core.mail.send_mail().

The subject, message, from_email and recipient_list parametersare required.

  • subject: A string.
  • message: A string.
  • from_email: A string.
  • recipient_list: A list of strings, each an email address. Eachmember of recipient_list will see the other recipients in the "To:"field of the email message.
  • fail_silently: A boolean. When it's False, send_mail() will raisean smtplib.SMTPException if an error occurs. See the smtplibdocs for a list of possible exceptions, all of which are subclasses ofSMTPException.
  • auth_user: The optional username to use to authenticate to the SMTPserver. If this isn't provided, Django will use the value of theEMAIL_HOST_USER setting.
  • auth_password: The optional password to use to authenticate to theSMTP server. If this isn't provided, Django will use the value of theEMAIL_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 backendsfor more details.
  • htmlmessage: If html_message is provided, the resulting email will be a_multipart/alternative email with message as thetext/plain content type and htmlmessage as the_text/html content type.
    The return value will be the number of successfully delivered messages (whichcan be 0 or 1 since it can only send one message).

send_mass_mail()

  • sendmass_mail(_datatuple, fail_silently=False, auth_user=None, auth_password=None, connection=None)[源代码]
  • django.core.mail.send_mass_mail() is intended to handle mass emailing.

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

  1. (subject, message, from_email, recipient_list)

fail_silently, auth_user and auth_password have the same functionsas in send_mail().

Each separate element of datatuple results in a separate email message.As in send_mail(), recipients in the samerecipient_list will all see the other addresses in the email messages'"To:" field.

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

  1. message1 = ('Subject here', 'Here is the message', 'from@example.com', ['first@example.com', 'other@example.com'])
  2. message2 = ('Another Subject', 'Here is another message', 'from@example.com', ['second@test.com'])
  3. 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() andsend_mail() is thatsend_mail() opens a connection to the mail servereach time it's executed, while send_mass_mail() usesa single connection for all of its messages. This makessend_mass_mail() slightly more efficient.

mail_admins()

  • mailadmins(_subject, message, fail_silently=False, connection=None, html_message=None)[源代码]
  • django.core.mail.mail_admins() is a shortcut for sending an email to thesite admins, as defined in the ADMINS setting.

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

The "From:" header of the email will be the value of theSERVER_EMAIL setting.

This method exists for convenience and readability.

If htmlmessage is provided, the resulting email will be a_multipart/alternative email with message as thetext/plain content type and htmlmessage as the_text/html content type.

mail_managers()

  • mailmanagers(_subject, message, fail_silently=False, connection=None, html_message=None)[源代码]
  • django.core.mail.mail_managers() is just like mail_admins(), except itsends an email to the site managers, as defined in the MANAGERSsetting.

示例

This sends a single email to john@example.com and jane@example.com, with themboth appearing in the "To:":

  1. send_mail(
  2.     'Subject',
  3.     'Message.',
  4.     'from@example.com',
  5.     ['john@example.com', 'jane@example.com'],
  6. )

This sends a message to john@example.com and jane@example.com, with them bothreceiving a separate email:

  1. datatuple = (
  2.     ('Subject', 'Message.', 'from@example.com', ['john@example.com']),
  3.     ('Subject', 'Message.', 'from@example.com', ['jane@example.com']),
  4. )
  5. send_mass_mail(datatuple)

Preventing header injection

Header injection is a security exploit in which an attacker inserts extraemail headers to control the "To:" and "From:" in email messages that yourscripts generate.

The Django email functions outlined above all protect against header injectionby forbidding newlines in header values. If any subject, from_email orrecipient_list contains a newline (in either Unix, Windows or Mac style),the email function (e.g. send_mail()) will raisedjango.core.mail.BadHeaderError (a subclass of ValueError) and, hence,will not send the email. It's your responsibility to validate all data beforepassing it to the email functions.

If a message contains headers at the start of the string, the headers willsimply be printed as the first bit of the email message.

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

  1. from django.core.mail import BadHeaderError, send_mail
  2. from django.http import HttpResponse, HttpResponseRedirect
  3.  
  4. def send_email(request):
  5.     subject = request.POST.get('subject', '')
  6.     message = request.POST.get('message', '')
  7.     from_email = request.POST.get('from_email', '')
  8.     if subject and message and from_email:
  9.         try:
  10.             send_mail(subject, message, from_email, ['admin@example.com'])
  11.         except BadHeaderError:
  12.             return HttpResponse('Invalid header found.')
  13.         return HttpResponseRedirect('/contact/thanks/')
  14.     else:
  15.         # In reality we'd use a form class
  16.         # to get proper validation errors.
  17.         return HttpResponse('Make sure all fields are entered and valid.')

The EmailMessage class

Django's send_mail() andsend_mass_mail() functions are actually thinwrappers that make use of the EmailMessage class.

Not all features of the EmailMessage class areavailable through the send_mail() and relatedwrapper functions. If you wish to use advanced features, such as BCC'edrecipients, file attachments, or multi-part email, you'll need to createEmailMessage instances directly.

注解

This is a design feature. send_mail() andrelated functions were originally the only interface Django provided.However, the list of parameters they accepted was slowly growing overtime. It made sense to move to a more object-oriented design for emailmessages and retain the original functions only for backwardscompatibility.

EmailMessage is responsible for creating the emailmessage itself. The email backend is thenresponsible for sending the email.

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

EmailMessage Objects

  • class EmailMessage[源代码]

  • The EmailMessage class is initialized with thefollowing parameters (in the given order, if positional arguments are used).All parameters are optional and can be set at any time prior to calling thesend() 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 andFred <fred@example.com> forms are legal. If omitted, theDEFAULT_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 whensending the email.
  • connection: An email backend instance. Use this parameter ifyou want to use the same connection for multiple messages. If omitted, anew connection is created when send() is called.
  • attachments: A list of attachments to put on the message. These canbe either MIMEBase instances, or (filename,
    content, mimetype)     triples.
  • headers: A dictionary of extra headers to put on the message. Thekeys are the header name, values are the header values. It's up to thecaller to ensure header names and values are in the correct format foran email message. The corresponding attribute is extra_headers.
  • cc: A list or tuple of recipient addresses used in the "Cc" headerwhen sending the email.
  • reply_to: A list or tuple of recipient addresses used in the "Reply-To"header when sending the email.
    例如:
  1. from django.core.mail import EmailMessage
  2.  
  3. email = EmailMessage(
  4.     'Hello',
  5.     'Body goes here',
  6.     'from@example.com',
  7.     ['to1@example.com', 'to2@example.com'],
  8.     ['bcc@example.com'],
  9.     reply_to=['another@example.com'],
  10.     headers={'Message-ID': 'foo'},
  11. )

The class has the following methods:

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

  • message() constructs a django.core.mail.SafeMIMEText object (asubclass of Python's MIMEText class) or adjango.core.mail.SafeMIMEMultipart object holding the message to besent. If you ever need to extend theEmailMessage class, you'll probably want tooverride 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. Thisis another method you might need to override when subclassing, because theSMTP server needs to be told the full list of recipients when the messageis sent. If you add another way to specify recipients in your class, theyneed 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 aMIMEBase instance. This will be inserted directlyinto the resulting message.

    • Alternatively, you can pass attach() three arguments:filename, content and mimetype. filename is the nameof the file attachment as it will appear in the email, content isthe data that will be contained inside the attachment andmimetype is the optional MIME type for the attachment. If youomit mimetype, the MIME content type will be guessed from thefilename of the attachment.

例如:

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

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

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

In addition, message/rfc822 attachments will no longer bebase64-encoded in violation of RFC 2046#section-5.2.1, which can causeissues with displaying the attachments in Evolution and Thunderbird.

  • attach_file() creates a new attachment using a file from yourfilesystem. 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, itwill be guessed from the filename. The simplest use would be:
  1. message.attach_file('/images/weather_map.png')

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

Sending alternative content types

It can be useful to include multiple versions of the content in an email; theclassic example is to send both text and HTML versions of a message. WithDjango's email library, you can do this using the EmailMultiAlternativesclass. This subclass of EmailMessage has anattach_alternative() method for including extra versions of the messagebody 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:

  1. from django.core.mail import EmailMultiAlternatives
  2.  
  3. subject, from_email, to = 'hello', 'from@example.com', 'to@example.com'
  4. text_content = 'This is an important message.'
  5. html_content = '<p>This is an <strong>important</strong> message.</p>'
  6. msg = EmailMultiAlternatives(subject, text_content, from_email, [to])
  7. msg.attach_alternative(html_content, "text/html")
  8. msg.send()

By default, the MIME type of the body parameter in anEmailMessage is "text/plain". It is goodpractice to leave this alone, because it guarantees that any recipient will beable to read the email, regardless of their mail client. However, if you areconfident that your recipients can handle an alternative content type, you canuse the content_subtype attribute on theEmailMessage class to change the main content type.The major type will always be "text", but you can change thesubtype. For example:

  1. msg = EmailMessage(subject, html_content, from_email, [to])
  2. msg.content_subtype = "html"  # Main content is now text/html
  3. 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 ofEmailMessage objects. If the connection isnot open, this call will implicitly open the connection, and close theconnection afterwards. If the connection is already open, it will beleft open after mail has been sent.
    It can also be used as a context manager, which will automatically callopen() and close() as needed:
  1. from django.core import mail
  2.  
  3. with mail.get_connection() as connection:
  4.     mail.EmailMessage(
  5.         subject1, body1, from1, [to1],
  6.         connection=connection,
  7.     ).send()
  8.     mail.EmailMessage(
  9.         subject2, body2, from2, [to2],
  10.         connection=connection,
  11.     ).send()

Obtaining an instance of an email backend

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

  • getconnection(_backend=None, fail_silently=False, *args, **kwargs)[源代码]
  • By default, a call to get_connection() will return an instance of theemail backend specified in EMAIL_BACKEND. If you specify thebackend 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 processwill be silently ignored.

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

Django ships with several email sending backends. With the exception of theSMTP backend (which is the default), these backends are only useful duringtesting and development. If you have special email sending requirements, youcan 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 theargument is None:

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

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

Console backend

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

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

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

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

File backend

The file backend writes emails to a file. A new file is created for each newsession that is opened on this backend. The directory to which the files arewritten is either taken from the EMAIL_FILE_PATH setting or fromthe file_path keyword when creating a connection withget_connection().

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

  1. EMAIL_BACKEND = 'django.core.mail.backends.filebased.EmailBackend'
  2. 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 aconvenience that can be used during development.

In-memory backend

The 'locmem' backend stores messages in a special attribute of thedjango.core.mail module. The outbox attribute is created when thefirst message is sent. It's a list with anEmailMessage instance for each message that wouldbe sent.

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

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

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

Dummy backend

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

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

This backend is not intended for use in production — it is provided as aconvenience 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 emailbackend. The EMAIL_BACKEND setting in your settings file is thenthe Python import path for your backend class.

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

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 anddestroying 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() takesa 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() thatreturns a list of EmailMessage objects representingsome periodic email you wish to send out, you could send these emails usinga single call to send_messages:

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

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

The second approach is to use the open() and close() methods on theemail backend to manually control the connection. send_messages() will notmanually open or close the connection if it is already open, so if youmanually open the connection, you can control when it is closed. For example:

  1. from django.core import mail
  2. connection = mail.get_connection()
  3.  
  4. # Manually open the connection
  5. connection.open()
  6.  
  7. # Construct an email message that uses the connection
  8. email1 = mail.EmailMessage(
  9.     'Hello',
  10.     'Body goes here',
  11.     'from@example.com',
  12.     ['to1@example.com'],
  13.     connection=connection,
  14. )
  15. email1.send() # Send the email
  16.  
  17. # Construct two more messages
  18. email2 = mail.EmailMessage(
  19.     'Hello',
  20.     'Body goes here',
  21.     'from@example.com',
  22.     ['to2@example.com'],
  23. )
  24. email3 = mail.EmailMessage(
  25.     'Hello',
  26.     'Body goes here',
  27.     'from@example.com',
  28.     ['to3@example.com'],
  29. )
  30.  
  31. # Send the two emails in a single call -
  32. connection.send_messages([email2, email3])
  33. # The connection was already open so send_messages() doesn't close it.
  34. # We need to manually close the connection.
  35. connection.close()

Configuring email for development

There are times when you do not want Django to send emails atall. For example, while developing a website, you probably don't wantto send out thousands of emails — but you may want to validate thatemails 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 theconsole email backend. This backendredirects all email to stdout, allowing you to inspect the content of mail.

The file email backend can also be usefulduring development — this backend dumps the contents of every SMTP connectionto a file that can be inspected at your leisure.

Another approach is to use a "dumb" SMTP server that receives the emailslocally and displays them to the terminal, but does not actually sendanything. Python has a built-in way to accomplish this with a single command:

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

This command will start a simple SMTP server listening on port 1025 oflocalhost. This server simply prints to standard output all email headers andthe email body. You then only need to set the EMAIL_HOST andEMAIL_PORT accordingly. For a more detailed discussion of SMTPserver 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.