一开始写的代码

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import smtplib
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from flask import Flask, request

MAIL_SERVER = 'smtp.163.com'
MAIL_USERNAME = 'my@163.com'
MAIL_PASSWORD = 'mypassword'
MAIL_PORT = 25
MAIL_NAME = '冰风漫天'
MAIL_ADDRESS = 'my@163.com'

def send_mail(subject, msg, receivers, cc=None, files=None):
    message = MIMEMultipart('alternative')
    mail_from = '{}<{}>'.format(MAIL_NAME, MAIL_ADDRESS)
    message['From'] = mail_from
    if cc:
        cc = set(cc)
        message['Cc'] = ','.join(cc)
    message['To'] = ','.join(receivers)
    message['Subject'] = subject
    message.attach(MIMEText(msg, 'plain', 'utf-8'))
    if MAIL_PORT == 25:
        smtp_obj = smtplib.SMTP()
    else:
        smtp_obj = smtplib.SMTP_SSL()
    if files:
        for file in files.values():
            msg_file = MIMEText(file.stream.read(), 'base64', 'utf8')
            msg_file.add_header('content-disposition', 'attachment', filename=file.filename)
            message.attach(msg_file)
    smtp_obj.connect(MAIL_SERVER)
    smtp_obj.login(MAIL_USERNAME, MAIL_PASSWORD)
    smtp_obj.sendmail(mail_from, receivers, message.as_string())


app = Flask(__name__)

@app.route('/', methods=['POST'])
def index():
    subject = request.form.get('subject')
    msg = request.form.get('msg')
    receivers = request.form.get('receivers')
    send_mail(subject, msg, receivers, files=request.files)
    return '1'

app.run()

请求方式

import requests
requests.post("http://127.0.0.1:5000/",data={"subject":u"发个邮件2","msg":"qweasd","receivers":["youmail@163.com"]},files={'file1':('filename1.txt','文件内容1'),'file2':('filename2.txt','file data2')})

存在两个问题：
1.当收件人有多个时，只有一个人能收到
2.部分邮件服务器上接收邮件不正常

解决方案：
问题1：把receivers = request.form.get(‘receivers’)改成receivers = request.form.getlist(‘receivers’)
问题2：把message = MIMEMultipart(‘alternative’)改成message = MIMEMultipart(‘mixed’)

最后的代码如下：

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import smtplib
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from flask import Flask, request

MAIL_SERVER = 'smtp.163.com'
MAIL_USERNAME = 'my@163.com'
MAIL_PASSWORD = 'mypassword'
MAIL_PORT = 25
MAIL_NAME = '冰风漫天'
MAIL_ADDRESS = 'my@163.com'

def send_mail(subject, msg, receivers, cc=None, files=None):
    message = MIMEMultipart('mixed')
    mail_from = '{}<{}>'.format(MAIL_NAME, MAIL_ADDRESS)
    message['From'] = mail_from
    if cc:
        cc = set(cc)
        message['Cc'] = ','.join(cc)
    message['To'] = ','.join(receivers)
    message['Subject'] = subject
    message.attach(MIMEText(msg, 'plain', 'utf-8'))
    if MAIL_PORT == 25:
        smtp_obj = smtplib.SMTP()
    else:
        smtp_obj = smtplib.SMTP_SSL()
    if files:
        for file in files.values():
            msg_file = MIMEText(file.stream.read(), 'base64', 'utf8')
            msg_file.add_header('content-disposition', 'attachment', filename=file.filename)
            message.attach(msg_file)
    smtp_obj.connect(MAIL_SERVER)
    smtp_obj.login(MAIL_USERNAME, MAIL_PASSWORD)
    smtp_obj.sendmail(mail_from, receivers, message.as_string())


app = Flask(__name__)

@app.route('/', methods=['POST'])
def index():
    subject = request.form.get('subject')
    msg = request.form.get('msg')
    receivers = request.form.getlist('receivers')
    send_mail(subject, msg, receivers, files=request.files)
    return '1'

app.run()