Python 3.7 smtplib sendmail sends only to first recipient in list

Question

I've gone through many SO posts and smtplib documentation, everything seems to be correct, but mail is sent to only first recipient in the list

Note: I'm using Python3.7, I've tried from Python 2.6 also, In below case mail is getting delivered only to very first recipient in receiver

Below is my code:

import smtplib
from email.mime.text import MIMEText


sender='from@domain.com'
receiver=['email1@domain.com', 'email2@domain.com', 'email3@domain.com']
msg = MIMEText("message")
msg['Subject'] = "Test Email"
msg['From'] = sender
msg['To'] = ",".join(receiver)

server = smtplib.SMTP("smtp.domain", 25)
sever.sendmail(sender, receiver, msg.as_string())
server.quit()

Answer 1

Instead of

sever.sendmail(sender, receiver, msg.as_string())

use

server.send_message(msg)

SMTP.send_message() is a method for sending email.message.Message objects which will use the sender and receiver specified in the Message object. In your case that would be the variable msg (MIMEText is a subclass of Message).

I don't know why, I had a similar issue when using it the way you did. Probably because to_addrs are specified twice as as_string() adds it to the message body, what happens later I don't know.

to_addrs in SMTP.sendmail() is described as: "A list of addresses to send this mail to. A bare string will be treated as a list with 1 address.", so that was fine.