I am getting an “error: ValueError: Cannot convert mixed to alternative.”
I get this error when I insert the open image and msg.add_attachment block (highlighted in btw #### ####). Without it, the code runs fine. I need to send the email as html and with the image attachment.
import osimport imghdrfrom email.message import EmailMessageimport smtplibEMAIL_ADDRESS = os.environ.get('EMAIL-USER')EMAIL_PASSWORD = os.environ.get('EMAIL-PASS')Message0 = "HelloWorld1"Message1 = "HelloWorld2"msg = EmailMessage()msg['Subject'] = 'Hello WORLD'msg['From'] = EMAIL_ADDRESSmsg['To'] = EMAIL_ADDRESSmsg.set_content('This is a plain text email, see HTML format')########################################################################with open('screenshot.png', 'rb') as f: file_data = f.read() file_type = imghdr.what(f.name) file_name = f.namemsg.add_attachment(file_data, maintype='image', subtype=file_type, filename=file_name)#########################################################################msg.add_alternative(""" <!DOCTYPE html> <html> <body> <h1 style="color:Blue;">Hello World</h1> {Message0} {Message1} </body> </html> """.format(**locals()), subtype='html')with smtplib.SMTP_SSL('smtp.gmail.com', 465) as smtp: smtp.login(EMAIL_ADDRESS, EMAIL_PASSWORD) smtp.send_message(msg) print("email sent")For the end result, I need to be able to send an email via Python and attach images.
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Answer
An e-mail can consist of a single part, or it can be a multi-part message.
If it is a multi-part message, it will usually be either a multipart/alternative, or a multipart/mixed.
multipart/alternativemeans there are 2 or more versions of the same content (e.g. plain text and html)multipart/mixedis used when multiple different contents need to be packed together (e.g. an email and an attachment)
What actually happens when multipart is used is that email consists of a “multipart” container which contains additional parts, e.g. for text+html it is something like this:
multipart/alternativeparttext/plainparttext/htmlpart
In case of an email with attachment, you can have something like this:
multipart/mixedparttext/plainpartimage/pngpart
So, the container is either mixed or alternative, but cannot be both. So, how to have both? You can nest them, e.g.:
multipart/mixedpartmultipart/alternativeparttext/plainparttext/htmlpart
image/pngpart
So, now you have an email which consists of a message and an attachment, and the message has both plain text and html.
Now, in code, this is the basic idea:
msg = EmailMessage()msg['Subject'] = 'Subject'msg['From'] = 'from@email'msg['To'] = 'to@email'msg.set_content('This is a plain text')msg.add_attachment(b'xxxxxx', maintype='image', subtype='png', filename='image.png')# Now there are plain text and attachment.# HTML should be added as alternative to the plain text part:text_part, attachment_part = msg.iter_parts()text_part.add_alternative("<p>html contents</p>", subtype='html')BTW, you can then see what is in each part this way:
>>> plain_text_part, html_text_part = text_part.iter_parts()>>> print(plain_text_part)Content-Type: text/plain; charset="utf-8"Content-Transfer-Encoding: 7bitThis is a plain text>>> print(html_text_part)Content-Type: text/html; charset="utf-8"Content-Transfer-Encoding: 7bitMIME-Version: 1.0<p>html contents</p>>>> print(attachment_part)Content-Type: image/pngContent-Transfer-Encoding: base64Content-Disposition: attachment; filename="image.png"MIME-Version: 1.0eHh4eHh4>>> print(msg)Subject: SubjectFrom: from@emailTo: to@emailMIME-Version: 1.0Content-Type: multipart/mixed; boundary="===============2219697219721248811=="--===============2219697219721248811==Content-Type: multipart/alternative; boundary="===============5680305804901241482=="--===============5680305804901241482==Content-Type: text/plain; charset="utf-8"Content-Transfer-Encoding: 7bitThis is a plain text--===============5680305804901241482==Content-Type: text/html; charset="utf-8"Content-Transfer-Encoding: 7bitMIME-Version: 1.0<p>html contents</p>--===============5680305804901241482==----===============2219697219721248811==Content-Type: image/pngContent-Transfer-Encoding: base64Content-Disposition: attachment; filename="image.png"MIME-Version: 1.0eHh4eHh4--===============2219697219721248811==--