How to Send Emails to Multiple Recipients Using Python\'s smtplib.sendmail()?

Sending Email to Multiple Recipients using Python smtplib

When attempting to utilize Python's smtplib.sendmail to email multiple recipients, users often encounter issues. Despite specifying multiple addresses in the email header, only the first recipient receives the message.

This arises from a disparity in formatting expectations between the email.Message module and the smtplib.sendmail() function. The email.Message module accepts comma-delimited email addresses in the header, while sendmail() requires a list of addresses.

To effectively send email to multiple recipients using smtplib.sendmail, follow these steps:

1. Create an email message using the email.MIMEMultipart module.
2. Set the header fields ("From", "To", "Cc") to include multiple email addresses, separated by commas.
3. Set the "To" parameter in the sendmail() function to a list of recipient email addresses (obtainable by splitting the comma-separated header field).
4. Set the "From" parameter to the sender's email address.
5. Compose the email body using the email.MIMEText module. Attach the body to the email message.
6. Configure a connection to your SMTP server and send the email using sendmail().

Example code to send an email to multiple recipients using smtplib.sendmail:

<code class="python">from email.MIMEMultipart import MIMEMultipart
from email.MIMEText import MIMEText
import smtplib

msg = MIMEMultipart()
msg["Subject"] = "Example"
msg["From"] = "sender@example.com"
msg["To"] = "recipient1@example.com,recipient2@example.com,recipient3@example.com"
msg["Cc"] = "cc1@example.com,cc2@example.com"
body = MIMEText("example email body")
msg.attach(body)
smtp = smtplib.SMTP("mailhost.example.com", 25)
smtp.sendmail(msg["From"], msg["To"].split(",") + msg["Cc"].split(","), msg.as_string())
smtp.quit()</code>

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