MAIL_SERVER = 'smtp.domain.com'
TO_ADDRESS = 'you@gmail.com'
FROM_ADDRESS = 'email@domain.com'
REPLY_TO_ADDRESS = 'email2@domain2.com'
import smtplib
import email.mime.multipart
msg = email.mime.multipart.MIMEMultipart()
msg['to'] = TO_ADDRESS
msg['from'] = FROM_ADDRESS
msg['subject'] = 'testing reply-to header'
msg.add_header('reply-to', REPLY_TO_ADDRESS)
server = smtplib.SMTP(MAIL_SERVER)
server.sendmail(msg['from'], [msg['to']], msg.as_string())
Setting different reply-to message in Python email/smtplib