The email built-in Python module lets us easily construct email messages.
We'll start by using the email.message.EmailMessage class to create an email message.
>>> from email.message import EmailMessage
>>> message = EmailMessage()
>>> sender = "me@example.com"
>>> recipient = "you@example.com" >>> message['From'] = sender
>>> message['To'] = recipient
>>> message['Subject'] = 'Greetings from {} to {}!'.format(sender, recipient)
>>> print(message)
From: me@example.com
To: you@example.com
Subject: Greetings from me@example.com to you@example.com!
From, To, and Subject are examples of email header fields. They’re key-value pairs of labels and instructions used by email clients and servers to route and display the email. They’re separate from the email's message body, which is the main content of the message.
>>> body = """Hey there!. I'm learning to send emails using Python!"""
>>> message.set_content(body)
>>> print(message)
From: me@example.com
To: you@example.com
Subject: Greetings from me@example.com to you@example.com!
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Hey there! I'm learning to send email using Python!
The set_content() method automatically added a couple of headers that the email infrastructure will use when sending this message to another machine. The Content-Type and Content-Transfer-Encoding headers tell email clients and servers how to interpret the bytes in this email message into a string.
Email messages are made up completely of strings. When you add an attachment to an email, whatever type the attachment happens to be, it’s encoded as some form of text. The Multipurpose Internet Mail Extensions (MIME) standard is used to encode all sorts of files as text strings that can be sent via email.
In order for the recipient of your message to understand what to do with an attachment, we need to label the attachment with a MIME type and subtype to tell them what sort of file you’re sending. The Internet Assigned Numbers Authority (IANA) (iana.org) hosts a registry of valid MIME types. If you know the correct type and subtype of the files you’ll be sending, you can use those values directly. If you don't know, you can use the Python mimetypes module to make a good guess.
>>> attachment_path = "/tmp/image.png"
>>> attachment_filename = os.path.basename(attachment_path)
>>> import mimetypes
>>> mime_type, _ = mimetypes.guess_type(attachment_path)
>>> print(mime_type)
image/png
mime_type string contains the MIME type and subtype, separated by a slash. The EmailMessage type needs a MIME type and subtypes as separate strings.
>>> mime_type, mime_subtype = mime_type.split('/', 1)
>>> print(mime_type)
image
>>> print(mime_subtype)
png
Now add the attachment to mail and print it.
>>> with open(attachment_path, 'rb') as ap:
... message.add_attachment(ap.read(), maintype=mime_type, subtype=mime_subtype,
... filename=os.path.basename(attachment_path))
...
>>> print(message)
Output:
Content-Type: multipart/mixed; boundary="===============5350123048127315795=="
--===============5350123048127315795==
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Hey there! I'm learning to send email using Python!
--===============5350123048127315795==
Content-Type: image/png
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="image.png"
MIME-Version: 1.0
iVBORw0KGgoAAAANSUhEUgAAASIAAABSCAYAAADw69nDAAAACXBIWXMAAAsTAAALEwEAmpwYAAAg
AElEQVR4nO2dd3wUZf7HP8/M9k2nKIJA4BCUNJKgNJWIBUUgEggCiSgeVhA8jzv05Gc5z4KHiqin
eBZIIBDKIXggKIeCRCAhjQAqx4UiCARSt83uzDy/PzazTDZbwy4BnHde+9qZydNn97Pf5/uUIZRS
(... few lines deleted ...)
wgAAAABJRU5ErkJggg==
--===============5350123048127315795==--
The entire message can be serialized as a text string, including the image that we attached. The email message as a whole has the MIME type "multipart/mixed". Each part of the message has its own MIME type. The message body is still there as a "text/plain" part, and the image attachment is an "image/png" part.
Sending mail:
To send emails, our computers use the Simple Mail Transfer Protocol (SMTP). This protocol specifies how computers can deliver emails to each other. There are certain steps that need to be followed to do this correctly. But we won't do this manually. We’ll send the message using the built-in smtplib Python module.
>>> import smtplib
>>> mail_server = smtplib.SMTP_SSL('smtp.example.com')
>>> sender = "from-address@example.com" >>> password = "**********"
>>> mail_server.login(sender, password)
>>> mail_server.send_message(message)
>>> mail_server.quit()
