How to Send Email to Multiple Recipients Using Python's smtplib

Utilizing smtplib.sendmail to transmit emails to several recipients can be challenging. To successfully deliver messages to multiple addresses, follow these guidelines:

Set the Header with Comma-Delimited Email Addresses:

In the header of the email (msg["To"]), use a string of comma-separated email addresses instead of a single recipient address.

Utilize a List for sendmail to_addrs Parameter:

Rather than a string, the to_addrs argument of smtplib.sendmail() should be a list containing individual email addresses. These addresses can be obtained by splitting the comma-separated string in the header.

Consider the following code snippet as an illustration:

import smtplib
from email.MIMEMultipart import MIMEMultipart
from email.MIMEText import MIMEText

msg = MIMEMultipart()
msg["Subject"] = "Subject Line"
msg["From"] = "[email protected]"
msg["To"] = "[email protected], [email protected], [email protected]"
body = MIMEText("Body of the email")
msg.attach(body)

smtp = smtplib.SMTP("mailhost.example.com")
smtp.sendmail(msg["From"], msg["To"].split(","), msg.as_string())
smtp.quit()

Alternatively, you can use the following approach:

import smtplib
from email.mime.text import MIMEText

s = smtplib.SMTP('smtp.uk.xensource.com')
msg = MIMEText("""**Body of the email""")
sender = '[email protected]'
recipients = ['[email protected]', '[email protected]']
msg['Subject'] = "Subject Line"
msg['From'] = sender
msg['To'] = ", ".join(recipients)
s.sendmail(sender, recipients, msg.as_string())