Specify a sender when sending mail with Python (smtplib)

smtplib doesn't automatically include a From: header, so you have to put one in yourself:

message = 'From: [email protected]\nSubject: [PGS]: Results\n\nBlaBlaBla'

(In fact, smtplib doesn't include any headers automatically, but just sends the text that you give it as a raw message)

You can utilize the email.message.Message class, and use it to generate mime headers, including from:, to: and subject. Send the as_string() result via SMTP.

>>> from email import message
>>> m1=message.Message()
>>> m1.add_header('from','[email protected]')
>>> m1.add_header('to','[email protected]')
>>> m1.add_header('subject','test')
>>> m1.set_payload('test\n')
>>> m1.as_string()
'from: [email protected]\nto: [email protected]\nsubject: test\n\ntest\n'
>>> 

See this answer, it's working for me.

example code:

#send html email
import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.header import Header
from email.utils import formataddr

msg = MIMEMultipart('alternative')
msg['From'] = formataddr((str(Header('MyWebsite', 'utf-8')), '[email protected]'))
msg['To'] = '[email protected]'

html = "email contents"

# Record the MIME types of text/html.
msg.attach(MIMEText(html, 'html'))

# Send the message via local SMTP server.
s = smtplib.SMTP('localhost')

# sendmail function takes 3 arguments: sender's address, recipient's address
# and message to send - here it is sent as one string.
s.sendmail('[email protected]', '[email protected]', msg.as_string())
s.quit()

The "sender" you're specifying in this case is the envelope sender that is passed onto the SMTP server.

What your MUA (Mail User Agent - i.e. outlook/Thunderbird etc.) shows you is the "From:" header.

Normally, if I'm using smtplib, I'd compile the headers separately:

headers = "From: %s\nTo: %s\n\n" % (email_from, email_to)

The format of the From header is by convention normally "Name" <user@domain>

You should be including a "Message-Id" header and a "Reply-To" header as well in all communications. Especially since spam filters may pick up on the lack of these as a great probability that the mail is spam.

If you've got your mail body in the variable body, just compile the overall message with:

message = headers + body

Note the double newline at the end of the headers. It's also worth noting that SMTP servers should separate headers with newlines only (i.e. LF - linfeed). However, I have seen a Windows SMTP server or two that uses \r\n (i.e. CRLF). If you're on Windows, YMMV.