How to Send an Email in Python
The first good news about Python is that it has a built-in module for sending emails via SMTP in its standard library. No extra installations or tricks are required. You can import the module using the following statement:
To make sure that the module has been imported properly and get the full description of its classes and arguments, type in an interactive Python session:
At our next step, we will talk a bit about servers: choosing the right option and configuring it.
SMTP server for testing emails in Python
When creating a new app or adding any functionality, especially when doing it for the first time, it’s essential to experiment on a test server. Here is a brief list of reasons:
- You won’t hit your friends’ and customers’ inboxes. This is vital when you test bulk email sending or work with an email database.
- You won’t flood your own inbox with testing emails.
- Your domain won’t be blacklisted for spam. ### Local SMTP server If you prefer working in the local environment, the local SMTP debugging server might be an option. For this purpose, Python offers an smtpd module. It has a DebuggingServer feature, which will discard messages you are sending out and will print them to stdout. It is compatible with all operations systems.
Set your SMTP server to localhost:1025
python -m smtpd -n -c DebuggingServer localhost:1025 In order to run SMTP server on port 25, you’ll need root permissions:
sudo python -m smtpd -n -c DebuggingServer localhost:25 It will help you verify whether your code is working and point out the possible problems if there are any. However, it won’t give you the opportunity to check how your HTML email template is rendered.
Fake SMTP server
Fake SMTP server imitates the work of a real 3rd party web server. In further examples in this post, we will use Mailtrap. Beyond testing email sending, it will let us check how the email will be rendered and displayed, review the message raw data as well as will provide us with a spam report. Mailtrap is very easy to set up: you will need just copy the credentials generated by the app and paste them into your code.
Here is how it looks in practice:
import smtplib port = 2525 smtp_server = "smtp.mailtrap.io" login = "1a2b3c4d5e6f7g" # your login generated by Mailtrap password = "1a2b3c4d5e6f7g" # your password generated by Mailtrap Mailtrap makes things even easier. Go to the Integrations section in the SMTP settings tab and get the ready-to-use template of the simple message, with your Mailtrap credentials in it. It is the most basic option of instructing your Python script on who sends what to who is the sendmail() instance method:
The code looks pretty straightforward, right? Let’s take a closer look at it and add some error handling (see the #explanations in between). To catch errors, we use the “try” and “except” blocks. Refer to the documentation for the list of exceptions here.
# the first step is always the same: import all necessary components: import smtplib from socket import gaierror # now you can play with your code. Let’s define the SMTP server separately here: port = 2525 smtp_server = "smtp.mailtrap.io" login = "1a2b3c4d5e6f7g" # paste your login generated by Mailtrap password = "1a2b3c4d5e6f7g" # paste your password generated by Mailtrap # specify the sender’s and receiver’s email addresses sender = "from@example.com" receiver = "mailtrap@example.com" # type your message: use two newlines (\n) to separate the subject from the message body, and use 'f' to automatically insert variables in the text message = f"""\ Subject: Hi Mailtrap To: From: This is my first message with Python.""" try: #send your message with credentials specified above with smtplib.SMTP(smtp_server, port) as server: server.login(login, password) server.sendmail(sender, receiver, message) # tell the script to report if your message was sent or which errors need to be fixed print('Sent') except (gaierror, ConnectionRefusedError): print('Failed to connect to the server. Bad connection settings?') except smtplib.SMTPServerDisconnected: print('Failed to connect to the server. Wrong user/password?') except smtplib.SMTPException as e: print('SMTP error occurred: ' + str(e)) Once you get the Sent result in Shell, you should see your message in your Mailtrap inbox:
Sending HTML email
In most cases, you need to add some formatting, links, or images to your email notifications. We can simply put all of these with the HTML content. For this purpose, Python has an email package.
We will deal with the MIME message type, which is able to combine HTML and plain text. In Python, it is handled by the email.mime module.
It is better to write a text version and an HTML version separately, and then merge them with the MIMEMultipart(“alternative”) instance. It means that such a message has two rendering options accordingly. In case an HTML isn’t be rendered successfully for some reason, a text version will still be available.
# import the necessary components first import smtplib from email.mime.text import MIMEText from email.mime.multipart import MIMEMultipart port = 2525 smtp_server = "smtp.mailtrap.io" login = "1a2b3c4d5e6f7g" # paste your login generated by Mailtrap password = "1a2b3c4d5e6f7g" # paste your password generated by Mailtrap sender_email = "mailtrap@example.com" receiver_email = "new@example.com" message = MIMEMultipart("alternative") message["Subject"] = "multipart test" message["From"] = sender_email message["To"] = receiver_email # write the plain text part text = """\ Hi, Check out the new post on the Mailtrap blog: SMTP Server for Testing: Cloud-based or Local? /blog/2018/09/27/cloud-or-local-smtp-server/ Feel free to let us know what content would be useful for you!""" # write the HTML part html = """\ Hi,
Check out the new post on the Mailtrap blog:
SMTP Server for Testing: Cloud-based or Local?
Feel free to let us know what content would be useful for you!
""" # convert both parts to MIMEText objects and add them to the MIMEMultipart message part1 = MIMEText(text, "plain") part2 = MIMEText(html, "html") message.attach(part1) message.attach(part2) # send your email with smtplib.SMTP("smtp.mailtrap.io", 2525) as server: server.login(login, password) server.sendmail( sender_email, receiver_email, message.as_string() ) print('Sent') 
Sending emails with attachments in Python
The next step in mastering sending emails with Python is attaching files. Attachments are still the MIME objects but we need to encode them with the base64 module. A couple of important points about the attachments:
- Python lets you attach text files, images, audio files, and even applications. You just need to use the appropriate email class like email.mime.audio.MIMEAudio or email.mime.image.MIMEImage. For the full information, refer to this section of the Python documentation. Also, you can check the examples provided by Python for a better understanding.
- Remember about the file size: sending files over 20MB is a bad practice.
In transactional emails, the PDF files are the most frequently used: we usually get receipts, tickets, boarding passes, orders confirmations, etc. So let’s review how to send a boarding pass as a PDF file.
import smtplib # import the corresponding modules from email import encoders from email.mime.base import MIMEBase from email.mime.multipart import MIMEMultipart from email.mime.text import MIMEText port = 2525 smtp_server = "smtp.mailtrap.io" login = "1a2b3c4d5e6f7g" # paste your login generated by Mailtrap password = "1a2b3c4d5e6f7g" # paste your password generated by Mailtrap subject = "An example of boarding pass" sender_email = "mailtrap@example.com" receiver_email = "new@example.com" message = MIMEMultipart() message["From"] = sender_email message["To"] = receiver_email message["Subject"] = subject # Add body to email body = "This is an example of how you can send a boarding pass in attachment with Python" message.attach(MIMEText(body, "plain")) filename = "yourBP.pdf" # Open PDF file in binary mode # We assume that the file is in the directory where you run your Python script from with open(filename, "rb") as attachment: # The content type "application/octet-stream" means that a MIME attachment is a binary file part = MIMEBase("application", "octet-stream") part.set_payload(attachment.read()) # Encode to base64 encoders.encode_base64(part) # Add header part.add_header( "Content-Disposition", f"attachment; filename= ", ) # Add attachment to your message and convert it to string message.attach(part) text = message.as_string() # send your email with smtplib.SMTP("smtp.mailtrap.io", 2525) as server: server.login(login, password) server.sendmail( sender_email, receiver_email, text ) print('Sent') 
To attach several files, you can call the message.attach() method several times.
How to send an email with images
Images, even if they are a part of the message body, are attachments as well. There are three types of them: CID attachments (embedded as a MIME object), base64 images (inline embedding), and linked images. We have described their peculiarities, pros and cons, and compatibility with most email clients in this post.
For adding a CID attachment, we will create a MIME multipart message with MIMEImage component:
# import all necessary components import smtplib from email.mime.text import MIMEText from email.mime.image import MIMEImage from email.mime.multipart import MIMEMultipart port = 2525 smtp_server = "smtp.mailtrap.io" login = "1a2b3c4d5e6f7g" # paste your login generated by Mailtrap password = "1a2b3c4d5e6f7g" # paste your password generated by Mailtrap sender_email = "mailtrap@example.com" receiver_email = "new@example.com" message = MIMEMultipart("alternative") message["Subject"] = "CID image test" message["From"] = sender_email message["To"] = receiver_email # write the HTML part html = """\ """ part = MIMEText(html, "html") message.attach(part) # We assume that the image file is in the same directory that you run your Python script from fp = open('mailtrap.jpg', 'rb') image = MIMEImage(fp.read()) fp.close() # Specify the ID according to the img src in the HTML part image.add_header('Content-ID', '') message.attach(image) # send your email with smtplib.SMTP("smtp.mailtrap.io", 2525) as server: server.login(login, password) server.sendmail( sender_email, receiver_email, message.as_string() ) print('Sent') 
The CID image is shown both as a part of the HTML message and as an attachment. Messages with this image type are often considered spam: check the Analytics tab in Mailtrap to see the spam rate and recommendations on its improvement. Many email clients – Gmail in particular – don’t display CID images in most cases. So let’s review how to embed a base64 encoded image.
Here we will use base64 module and experiment with the same image file:
(look up the code here)
Output:
Now the image is embedded into the HTML message and is not available as attached file. Python has encoded our jpg image, and if we go to the HTML Source tab, we will see the long image data string in the img src.
How to send multiple emails in Python
Sending multiple emails to different recipients and making them personal is the special thing about emails in Python.
To add several more recipients, you can just type their addresses in separated by a comma, add CC and BCC. But if you work with a bulk email sending, Python will save you with loops.
One of the options is to create a database in a .csv format (we assume it is saved to the same folder as your Python script).
We often see our names in transactional or even promotional examples. Here is how we can make it with Python.
Let’s organize the list in a simple table with just two columns: name and email address. It should look like the following example:
#name,email
John Johnson,john@johnson.com
Peter Peterson,peter@peterson.com
The code below will open the file and loop over its rows line by line, replacing the with the value from the “name” column.
import csv, smtplib port = 2525 smtp_server = "smtp.mailtrap.io" login = "1a2b3c4d5e6f7g" # paste your login generated by Mailtrap password = "1a2b3c4d5e6f7g" # paste your password generated by Mailtrap message = """Subject: Order confirmation To: From: Hi , thanks for your order! We are processing it now and will contact you soon""" sender = "new@example.com" with smtplib.SMTP("smtp.mailtrap.io", 2525) as server: server.login(login, password) with open("contacts.csv") as file: reader = csv.reader(file) next(reader) # it skips the header row for name, email in reader: server.sendmail( sender, email, message.format(name=name, recipient=email, sender=sender) ) print(f'Sent to ') After running the script, we get the following response:
Sent to John Johnson Sent to Peter Peterson >>>