你需要在直接运行到STARTTLS之前说EHLO:

server = smtplib.SMTP('smtp.gmail.com:587')
server.ehlo()
server.starttls()

此外，您应该真正创建From:、To:和Subject:消息头，用空行与消息体分隔，并使用CRLF作为EOL标记。

E.g.

msg = "\r\n".join([
  "From: user_me@gmail.com",
  "To: user_you@gmail.com",
  "Subject: Just a message",
  "",
  "Why, oh why"
  ])

注意:

为了做到这一点，你需要在gmail帐户配置中启用“允许不太安全的应用程序”选项。否则，当gmail检测到一个非谷歌应用程序试图登录你的帐户时，你会得到一个“关键安全警报”。

import smtplib
server = smtplib.SMTP('smtp.gmail.com', 587)
server.ehlo()
server.starttls()
server.login("fromaddress", "password")
msg = "HI!"
server.sendmail("fromaddress", "receiveraddress", msg)
server.quit()

下面是一个Gmail API的例子。虽然比较复杂，但这是我发现在2019年唯一有效的方法。这个例子是从以下例子中获取并修改的:

https://developers.google.com/gmail/api/guides/sending

你需要通过谷歌的网站创建一个API接口的项目。接下来，你需要为你的应用程序启用GMAIL API。创建凭证，然后下载这些凭证，保存为credentials.json。

import pickle
import os.path
from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request

from email.mime.text import MIMEText
import base64

#pip install --upgrade google-api-python-client google-auth-httplib2 google-auth-oauthlib

# If modifying these scopes, delete the file token.pickle.
SCOPES = ['https://www.googleapis.com/auth/gmail.readonly', 'https://www.googleapis.com/auth/gmail.send']

def create_message(sender, to, subject, msg):
    message = MIMEText(msg)
    message['to'] = to
    message['from'] = sender
    message['subject'] = subject

    # Base 64 encode
    b64_bytes = base64.urlsafe_b64encode(message.as_bytes())
    b64_string = b64_bytes.decode()
    return {'raw': b64_string}
    #return {'raw': base64.urlsafe_b64encode(message.as_string())}

def send_message(service, user_id, message):
    #try:
    message = (service.users().messages().send(userId=user_id, body=message).execute())
    print( 'Message Id: %s' % message['id'] )
    return message
    #except errors.HttpError, error:print( 'An error occurred: %s' % error )

def main():
    """Shows basic usage of the Gmail API.
    Lists the user's Gmail labels.
    """
    creds = None
    # The file token.pickle stores the user's access and refresh tokens, and is
    # created automatically when the authorization flow completes for the first
    # time.
    if os.path.exists('token.pickle'):
        with open('token.pickle', 'rb') as token:
            creds = pickle.load(token)
    # If there are no (valid) credentials available, let the user log in.
    if not creds or not creds.valid:
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
        else:
            flow = InstalledAppFlow.from_client_secrets_file(
                'credentials.json', SCOPES)
            creds = flow.run_local_server(port=0)
        # Save the credentials for the next run
        with open('token.pickle', 'wb') as token:
            pickle.dump(creds, token)

    service = build('gmail', 'v1', credentials=creds)

    # Example read operation
    results = service.users().labels().list(userId='me').execute()
    labels = results.get('labels', [])

    if not labels:
        print('No labels found.')
    else:
        print('Labels:')
    for label in labels:
        print(label['name'])

    # Example write
    msg = create_message("from@gmail.com", "to@gmail.com", "Subject", "Msg")
    send_message( service, 'me', msg)

if __name__ == '__main__':
    main()

你同意OOP吗?

#!/usr/bin/env python


import smtplib

class Gmail(object):
    def __init__(self, email, password):
        self.email = email
        self.password = password
        self.server = 'smtp.gmail.com'
        self.port = 587
        session = smtplib.SMTP(self.server, self.port)        
        session.ehlo()
        session.starttls()
        session.ehlo
        session.login(self.email, self.password)
        self.session = session

    def send_message(self, subject, body):
        ''' This must be removed '''
        headers = [
            "From: " + self.email,
            "Subject: " + subject,
            "To: " + self.email,
            "MIME-Version: 1.0",
           "Content-Type: text/html"]
        headers = "\r\n".join(headers)
        self.session.sendmail(
            self.email,
            self.email,
            headers + "\r\n\r\n" + body)


gm = Gmail('Your Email', 'Password')

gm.send_message('Subject', 'Message')

def send_email(user, pwd, recipient, subject, body):
    import smtplib

    FROM = user
    TO = recipient if isinstance(recipient, list) else [recipient]
    SUBJECT = subject
    TEXT = body

    # Prepare actual message
    message = """From: %s\nTo: %s\nSubject: %s\n\n%s
    """ % (FROM, ", ".join(TO), SUBJECT, TEXT)
    try:
        server = smtplib.SMTP("smtp.gmail.com", 587)
        server.ehlo()
        server.starttls()
        server.login(user, pwd)
        server.sendmail(FROM, TO, message)
        server.close()
        print 'successfully sent the mail'
    except:
        print "failed to send mail"

如果你想使用端口465，你必须创建一个SMTP_SSL对象:

# SMTP_SSL Example
server_ssl = smtplib.SMTP_SSL("smtp.gmail.com", 465)
server_ssl.ehlo() # optional, called by login()
server_ssl.login(gmail_user, gmail_pwd)  
# ssl server doesn't support or need tls, so don't call server_ssl.starttls() 
server_ssl.sendmail(FROM, TO, message)
#server_ssl.quit()
server_ssl.close()
print 'successfully sent the mail'

意识到用Python发送电子邮件有多痛苦，所以我为它做了一个广泛的库。它也有Gmail预配置(所以你不需要记住Gmail的主机和端口):

from redmail import gmail
gmail.user_name = "you@gmail.com"
gmail.password = "<YOUR APPLICATION PASSWORD>"

# Send an email
gmail.send(
    subject="An example email",
    receivers=["recipient@example.com"],
    text="Hi, this is text body.",
    html="<h1>Hi, this is HTML body.</h1>"
)

当然你需要配置你的Gmail账号(别担心，很简单):

设置两步验证(如果尚未设置) 创建应用程序密码 将应用程序密码设置为gmail对象，完成!

红色邮件实际上是相当广泛的(包括附件，嵌入图像，发送与抄送和密件，模板与Jinja等)，应该是所有你需要从电子邮件发件人。它也经过了良好的测试和文档记录。我希望它对你有用。

如何安装:

pip install redmail

文档:https://red-mail.readthedocs.io/en/latest/

源代码:https://github.com/Miksus/red-mail

注意，Gmail不允许更改发送方。发件人地址永远是你。