Creating and sending HTML email with Python

When you want to send tidy e-mails for marketing or other purposes you quickly run into the solution of using html within e-mails. In this post we will show you a code snippet that allows you to send such a html e-mail using standard python libraries.

However, before we start you should know that there are quite a few articles and posts mentioning that creating html e-mails is a (very) bad idea. I believe it is ok sending out html e-mails these days; loads of support within e-mail clients has been added and you can see the number of html e-mails growing every day. MailChimp actually provide the ability to create HTML based emails so if they do it, why not you. You may be sending out these emails because its a busy period for your eCommerce shop. If that is the case I would recommend that read about our 5 best practices for eCommerce testing. However, there are a few caveats that you should be aware of! Lets list some of them first!..

CSS support

Obviously you want to use some CSS styles in your HTML e-mail. There are some differences with the support of CSS in an e-mail, support per css property can really differ per e-mail client/browser. Since it is really hard and not too much fun to try out all the different e-mail clients/portals you’d be better off to first see what html tags and css properties are actually supported. The best guide to this CSS Support maze in e-mail clients is probably this one.

When you are using CSS in your html e-mail, the best thing to do is to just put the CSS in a <style> tag in the <head>. Another possibility is to put a link to the CSS file but since that needs to be retrieved and might be blocked upon first view, so that is not the best solution. A problem here is that, as of writing, google gmail does not support a <style> tag or <link> to your CSS file in the <head>! Thus, if you want your style to be processed and visible in gmail, you have to include it in the html tags itself. Now, this is not the most ideal situation, but one thing you can do is to just put some minimal style in the html tags and put the rest in the CSS style tag. This approach has been used in the table below. This way, even when style tags are not supported you would still get the minimal ‘display tidyness’.

Catch e-mail clients where html e-mail is unsupported

With an html e-mail you have to change the “MIME type” of the email. Nearly all email clients support this nowadays, but it can still happen that you come across a client that doesnt. In the example you can see that, with a very simple setting, you can prevent the user from not receiving any feedback.

Always give a reference to the source/online example

Perhaps obvious, but it is advised to always have an example or reference to the content in the email online, and point to that. This way the receiver will not only be able to see the content in any situation, but you also have another option to drive the users to your website or service.

Reason and Un-subscribe

Another slightly obvious point; you should always give a reference to why someone receives the HTML e-mail (etc, subscribed to a newsletter..) so the receiver doesnt feel like he just received spam/unwanted marketing. Also an option to unsubscribe/stop receiving the emails should be included.

The example

import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
def py_mail(SUBJECT, BODY, TO, FROM):
    """With this function we send out our html email"""
    # Create message container - the correct MIME type is multipart/alternative here!
    MESSAGE = MIMEMultipart('alternative')
    MESSAGE['subject'] = SUBJECT
    MESSAGE['To'] = TO
    MESSAGE['From'] = FROM
    MESSAGE.preamble = """
Your mail reader does not support the report format.
Please visit us <a href="">online</a>!"""
    # Record the MIME type text/html.
    HTML_BODY = MIMEText(BODY, 'html')
    # Attach parts into message container.
    # According to RFC 2046, the last part of a multipart message, in this case
    # the HTML message, is best and preferred.
    # The actual sending of the e-mail
    server = smtplib.SMTP('')
    # Print debugging output when testing
    if __name__ == "__main__":
    # Credentials (if needed) for sending the mail
    password = "mypassword"
    server.sendmail(FROM, [TO], MESSAGE.as_string())
if __name__ == "__main__":
    """Executes if the script is run as main script (for testing purposes)"""
    email_content = """
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  <title>html title</title>
  <style type="text/css" media="screen">
        background-color: #AAD373;
        background-color: white;
<table style="border: blue 1px solid;">
<td class="cell">Cell 1.1</td>
<td class="cell">Cell 1.2</td>
<td class="cell">Cell 2.1</td>
<td class="cell"></td>
    TO = ''
    FROM =''
    py_mail("Test email subject", email_content, TO, FROM)

The example aftermath

The example requires you to change the FROM and TO email addresses and the password to send the email. If you do not use gmail to send the e-mail, you can probably find your smtp server settings here. The debugging option should give you a clear idea what the problem is, if something goes wrong regarding the sending process. There are also a lot of posts online about troubleshooting with python’s smtp lib.

When you execute the example and view the email in your gmail browser client you will see that the ‘in-tag-html’ styles are processed but not the style defined in the style tag. In other clients however, all the styles in the example are processed.

If all this technical talk seems a bit too much for you and you just need some way to ensure that your email campaigns are working with your order systems then get in touch with us. We are experts in eCommerce testing to help ensure that webshops perform correctly during those important periods like the holidays.

We provide:

  • Security testing to ensure no hackers break into your website.
  • Performance and load testing to make sure your website continues to work even when your successful marketing campaign attracts more customer than expected.
  • Functional testing to make sure your website works properly and doesn’t damage your reputation with potential customers.

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