python使用smtplib发送邮件

python要实现发送邮件的功能，需要使用smtplib库。

1. 过程大致如下:

1. 建立和SMTP邮件服务器的连接

# 默认端口25
smtp = smtplib.SMTP(host, port)
# 或者
smtp = smtplib.SMTP()
smtp.connect(host, port)

# 带SSL,默认端口465
smtp = smtp.SMTP_SSL()
smtp.connect(host, port)

2. 完成身份认证

# 对于163而言，第三方客户端登陆使用的是授权码而不是密码
smtp.login(username, password)

3. 发送邮件(必须明确发件人、收件人、主题、内容，而抄送人、密送人、附件、内嵌式图片等资源是可选的)

smtp.sendmail(from_addr, to_addrs, msg, mail_options=[], rcpt_options=[])

4. 结束会话

smtp.quit()

2. MIME相关知识介绍

MIME全称Multipurpose Internet Mail Extensions(多用途互联网邮件扩展)。是一个互联网标准，它扩展了电子邮件标准，使其能够支持:

• 非ASCII字符文本；
• 非文本格式附件（二进制、声音、图像等）；
• 由多部分（multiple parts）组成的消息体；
• 包含非ASCII字符的头信息（Header information）

此外，web中使用的HTTP协议也使用了MIMIE的框架，标准被扩展为互联网媒体类型。

MIME头部信息:

MIME版本: 目前版本1.0

MIME-Version: 1.0

内容类型(Content-Type),用于指定消息类型。 形式如下:

Content-Type: [type]/[subtype]; parameter

type有以下形式:

• Text: 文本消息， 可以使用charset参数指定字符集;
• Multipart: 用于连接消息体的多个部分构成一个消息，这些部分可以是不同类型的数据；
• Application：用于传输应用程序数据或者二进制数据；
• Message：用于包装一个E-mail消息；
• Image：用于传输静态图片数据；
• Audio：用于传输音频数据；
• Video：用于传输动态影像数据，可以是与音频编辑在一起的视频数据格式

常见的文件扩展名与Content-Type对应关系如下:

文件扩展名	Content-Type
.txt	text/plain
.html	text/html
.xhtml	application/xhtml+xml
.css	text/css
.js	application/javascript
.xml	application/atom+xml
.json	application/json
.jpg	image/jpeg
.png	image/png
.gif	image/gif
.mp3	audio/mpeg3
.mp4	video/mp4
.wav	audio/wav
.avi	video/avi
.doc	application/msword
.docx	application/vnd.openxmlformats-officedocument.wordprocessingml.document
.xls	application/vnd.ms-excel
.xlsx	application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
.ppt	application/vnd.ms-powerpoint
.pptx	application/vnd.openxmlformats-officedocument.presentationml.presentation
.pdf	application/pdf
.rar	application/x-rar-compressed
.zip	application/x-compressed
.tar	application/x-tar
.gz	application/x-compressed
.bz2	application/x-bzip2
表示任意二进制数据	application/octet-stream
使用HTTP的POST方法提交表单	application/x-www-form-urlencoded
主要用于表单提交时伴随文件上传的场合	multipart/form-data

Text默认是text/plain，Application默认是application/octet-stream而Multipart默认情况下被看作multipart/mixed。

内容传输编码(Content-Transfer-Encoding)

Content-Transfer-Encoding: [mechanism]

其中，mechanism的值可以指定为“7bit”，“8bit”，“binary”，“quoted-printable”，“base64”

MIME信息剖析

一封普通的文本邮件的信息包含一个头部分（例如：From、To、Subject 等等）和一个体部分。体部分通常为单体类型（例如：text、image、audio、video、application 等等）或是复合类型（即：multipart）。头部分和体部分之间用一个空行进行分隔，并且体部分的类型由信头内容类型字段 Content-Type 描述。

信头含义 (Headers)

域名	含义
Content-Type	内容的类型
MIME-Version	MIME 版本
Content-Transfer-Encoding	内容的传输编码方式
From	发件人地址
To	收件人地址
Cc	抄送地址
Bcc	暗送地址
Date	日期和时间
Subject	主题
Received	传输路径
Return-Path	回复地址
Delivered-To	发送地址
Reply-To	回复地址
Message-ID	消息 ID

信体部分

• 邮件中常见的简单类型有 text/plain(纯文本)和 text/html(超文本)。

• 复杂的邮件内容格式采用 multipart 类型，可以包括纯文本/超文本(alternative)、内嵌资源（图片)(related)、附件类型(mixed)等等。

  multipart 类型的邮件体被分为多个段，每个段又包含段头和段体两部分，这两部分之间也以空行分隔。

信体头含义

域名	含义
Content-Type	段体的类型
Content-Transfer-Encoding	段体的传输编码方式
Content-Disposition	段体的位置,内嵌(inline)或附件(attachment)
Content-ID	段体的 ID, 唯一标识
Content-Location	段体的位置(路径)
Content-Base	段体的基位置

常见的 multipart 类型有三种：multipart/mixed, multipart/related 和 multipart/alternative。

复合类型层次关系示例图：

multipart 诸类型的共同特征是，在段头指定 boundary 参数字符串，段体内的每个子段以此字符串定界。

所有的子段都以 --boundary 行开始，父段则以 --boundary-- 行结束。段与段之间也以空行分隔。

例子:

1) 发送纯文本文件:

Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: base64

aGVsbG8gd29ybGQK5L2g5aW95LiW55WM

2)发送包含富文本的邮件:

Content-Type: multipart/alternative;
  boundary="----=ALIBOUNDARY_14343_4f941940_5a9a0b10_90106"

------=ALIBOUNDARY_14343_4f941940_5a9a0b10_90106
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: base64

aGVsbG8gd29ybGTkvaDlpb3kuJbnlYw=
------=ALIBOUNDARY_14343_4f941940_5a9a0b10_90106
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: base64

PGRpdiBjbGFzcz0iX19hbGl5dW5fZW1haWxfYm9keV9ibG9jayI+PGRpdiAgc3R5bGU9ImNsZWFy
OmJvdGg7Ij48c3BhbiAgc3R5bGU9ImZvbnQtZmFtaWx5OlRhaG9tYSxBcmlhbCxTVEhlaXRpLFNp
bVN1bjtmb250LXNpemU6MTQuMHB4O2NvbG9yOiMwMDAwMDA7Ij5oZWxsbyB3b3JsZDwvc3Bhbj48
L2Rpdj48ZGl2ICBzdHlsZT0iY2xlYXI6Ym90aDsiPjxzcGFuICBzdHlsZT0iZm9udC1mYW1pbHk6
VGFob21hLEFyaWFsLFNUSGVpdGksU2ltU3VuO2NvbG9yOiMwMDAwMDA7YmFja2dyb3VuZC1jb2xv
cjojZmYwMDAwO2ZvbnQtc2l6ZTozMi4wcHg7Ij7kvaDlpb3kuJbnlYw8L3NwYW4+PC9kaXY+PC9k
aXY+
------=ALIBOUNDARY_14343_4f941940_5a9a0b10_90106--

”aGVsbG8gd29ybGTkvaDlpb3kuJbnlYw=" base64前明文:

hello world你好世界

"

PGRpdiBjbGFzcz0iX19hbGl5dW5fZW1haWxfYm9keV9ibG9jayI+PGRpdiAgc3R5bGU9ImNsZWFy
OmJvdGg7Ij48c3BhbiAgc3R5bGU9ImZvbnQtZmFtaWx5OlRhaG9tYSxBcmlhbCxTVEhlaXRpLFNp
bVN1bjtmb250LXNpemU6MTQuMHB4O2NvbG9yOiMwMDAwMDA7Ij5oZWxsbyB3b3JsZDwvc3Bhbj48
L2Rpdj48ZGl2ICBzdHlsZT0iY2xlYXI6Ym90aDsiPjxzcGFuICBzdHlsZT0iZm9udC1mYW1pbHk6
VGFob21hLEFyaWFsLFNUSGVpdGksU2ltU3VuO2NvbG9yOiMwMDAwMDA7YmFja2dyb3VuZC1jb2xv
cjojZmYwMDAwO2ZvbnQtc2l6ZTozMi4wcHg7Ij7kvaDlpb3kuJbnlYw8L3NwYW4+PC9kaXY+PC9k
aXY+" 明文:

<div class="__aliyun_email_body_block"><div  style="clear:both;"><span  style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14.0px;color:#000000;">hello world</span></div>
<div  style="clear:both;"><span  style="font-family:Tahoma,Arial,STHeiti,SimSun;color:#000000;background-color:#ff0000;font-size:32.0px;">你好世界</span></div></div>

3) 将图片内嵌:

Content-Type: multipart/related;
  boundary="----=ALIBOUNDARY_25467_4f851940_5a9a032e_8ff9d"

------=ALIBOUNDARY_25467_4f851940_5a9a032e_8ff9d
Content-Type: multipart/alternative;
  boundary="----=ALIBOUNDARY_25467_4f851940_5a9a032e_8ff9e"

------=ALIBOUNDARY_25467_4f851940_5a9a032e_8ff9e
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: base64

6L+Z5pivcHl0aG9u55qEbG9nb8KgCg==     
------=ALIBOUNDARY_25467_4f851940_5a9a032e_8ff9e
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: base64

PGRpdiBjbGFzcz0iX19hbGl5dW5fZW1haWxfYm9keV9ibG9jayI+PGRpdiAgc3R5bGU9ImNsZWFy
OmJvdGg7Ij48c3BhbiAgc3R5bGU9ImZvbnQtZmFtaWx5OlRhaG9tYSxBcmlhbCxTVEhlaXRpLFNp
bVN1bjtmb250LXNpemU6MTQuMHB4O2NvbG9yOiMwMDAwMDA7Ij7ov5nmmK9weXRob27nmoRsb2dv
PC9zcGFuPjwvZGl2PjxkaXYgIHN0eWxlPSJjbGVhcjpib3RoOyI+PHNwYW4gIHN0eWxlPSJmb250
LWZhbWlseTpUYWhvbWEsQXJpYWwsU1RIZWl0aSxTaW1TdW47Zm9udC1zaXplOjE0LjBweDtjb2xv
cjojMDAwMDAwOyI+PGltZyAgc3JjPSJjaWQ6X19hbGl5dW4xNTIwMDQyNzk4MjEzOTg3MjEiPiZu
YnNwOzxiciA+PC9zcGFuPjwvZGl2PjwvZGl2Pg==
------=ALIBOUNDARY_25467_4f851940_5a9a032e_8ff9e--

------=ALIBOUNDARY_25467_4f851940_5a9a032e_8ff9d
Content-Type: application/octet-stream
Content-ID: <__aliyun152004279821398721>
Content-Disposition: inline; filename="=?UTF-8?B?cHl0aG9uLWxvZ28ucG5n?="
Content-Transfer-Encoding: base64

下面多行是图片二进制数据base64编码后的数据
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

------=ALIBOUNDARY_25467_4f851940_5a9a032e_8ff9d--

"6L+Z5pivcHl0aG9u55qEbG9nb8KgCg==" 是经过base64编码后的数据，明文为:

这是python的logo

"

PGRpdiBjbGFzcz0iX19hbGl5dW5fZW1haWxfYm9keV9ibG9jayI+PGRpdiAgc3R5bGU9ImNsZWFy
OmJvdGg7Ij48c3BhbiAgc3R5bGU9ImZvbnQtZmFtaWx5OlRhaG9tYSxBcmlhbCxTVEhlaXRpLFNp
bVN1bjtmb250LXNpemU6MTQuMHB4O2NvbG9yOiMwMDAwMDA7Ij7ov5nmmK9weXRob27nmoRsb2dv
PC9zcGFuPjwvZGl2PjxkaXYgIHN0eWxlPSJjbGVhcjpib3RoOyI+PHNwYW4gIHN0eWxlPSJmb250
LWZhbWlseTpUYWhvbWEsQXJpYWwsU1RIZWl0aSxTaW1TdW47Zm9udC1zaXplOjE0LjBweDtjb2xv
cjojMDAwMDAwOyI+PGltZyAgc3JjPSJjaWQ6X19hbGl5dW4xNTIwMDQyNzk4MjEzOTg3MjEiPiZu
YnNwOzxiciA+PC9zcGFuPjwvZGl2PjwvZGl2Pg==" 明文为:

<div class="__aliyun_email_body_block"><div  style="clear:both;"><span  style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14.0px;color:#000000;">
这是python的logo</span></div><div  style="clear:both;"><span  style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14.0px;color:#000000;">
<img  src="cid:__aliyun152004279821398721">&nbsp;<br ></span></div></div>

4) 发送带附件的邮件

Content-Type: multipart/mixed;
  boundary="----=ALIBOUNDARY_68661_4cbc5940_5a9a0f2a_90709"

This is a multi-part message in MIME format.

------=ALIBOUNDARY_68661_4cbc5940_5a9a0f2a_90709
Content-Type: multipart/alternative;
  boundary="----=ALIBOUNDARY_68661_4cbc5940_5a9a0f2a_9070a"

------=ALIBOUNDARY_68661_4cbc5940_5a9a0f2a_9070a
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: base64

5Y+R6YCB6ZmE5Lu25rWL6K+V
------=ALIBOUNDARY_68661_4cbc5940_5a9a0f2a_9070a
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: base64
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------=ALIBOUNDARY_68661_4cbc5940_5a9a0f2a_9070a--

------=ALIBOUNDARY_68661_4cbc5940_5a9a0f2a_90709
Content-Type: application/octet-stream
Content-Disposition: attachment; filename="=?UTF-8?B?5L2g5aW9d29ybGQudHh0?="
Content-Transfer-Encoding: base64

aGVsbG8gd29ybGQNCsTjusPKwL3n

------=ALIBOUNDARY_68661_4cbc5940_5a9a0f2a_90709--

multipart/alternative:

在同时提供多种消息格式，这些消息格式间是相互可替换的,如提供同一消息的多语言版本。

multipart/related:

添加内嵌资源时必须指定的Content-Type类型，通常配合Content-ID使用。

Content-ID头字段用于为“multipart/related” 组合消息中的内嵌资源指定一个唯一的标识符。在html格式的正文中使用这个唯一标识号来引用该内嵌资源。格式如下:

<img  src="cid:CONTENTID" />
# CONTENTID用具体的数值替换

multipart/mixed:

　　添加附件时必须指定的Content-Type类型, 配合Content-Disposition来获取上文文件的名称。

Content-Disposition: attachment; filename=”上传文件的文件名"
#  一般中文文件名都需要base64编码
#  以python_logo.png为例，base64编码后变为: cHl0aG9uX2xvZ28ucG5n
#  最后结果为:  =?UTF-8?B?cHl0aG9uLWxvZ28ucG5n?=

3. python中的MIME

参考: email.mime

MIMENonMultipart 作为中间类，主要用途是防止调用attach()方法

MIMEMultipart 与Conent-Type中的multipart对应，默认类型为multipart/mixed

MIMEApplication与Content-Type中的application对应，默认类型为application/octed-stream,默认编码类型为base64

MIMEText与Content-Type中的text对应，默认类型为text/plain。

身份认证发生错误:

smtplib.SMTPAuthenticationError: (535, 'Error: authentication failed')

原因分析:网易163邮箱需要启用授权码，并且使用授权码登录，而不是密码登录

1. 发送纯文本

import smtplib
from email.mime.text import MIMEText
from email.header import Header

host = "smtp.aliyun.com"
username = "u1@aliyun.com"
# 对于163邮箱使用授权码而不是密码登录
password = "xxxxxxxxxxxx"

# 接收人列表
receivers = ['q1@qq.com']
# 抄送人列表
cc_list = ['q2@qq.com']
# 密送人列表
bcc_list = ['q3@qq.com']
# 主题
subject = "阿里邮箱给qq邮箱发信"
# 正文
body = "Python 发送邮件测试"

sender = username
# 邮件正文
message = MIMEText(body, 'plain', 'utf-8')
# 发件人
message['From'] = sender
# 收件人
message['To'] = ",".join(receivers)   # 多个接收人之间要用逗号隔开
# 抄送人
message['Cc'] = ','.join(cc_list)
# 密送人
message['Bcc'] = ','.join(bcc_list)
# 主题
message['Subject'] = Header(subject, "utf-8")

try:
    smtp = smtplib.SMTP()
    smtp.set_debuglevel(1)  # 开启调试,方便观察和邮件服务器通信全过程
    smtp.connect(host)   # 默认端口是25
    # 登陆
    smtp.login(username, password)
    # 发送邮件
    # 邮件服务器在转发邮件的过程中，省略了Bcc项
    # To: Cc: Bcc: 只是一种表现形式，归根结底都是邮件的接收者,都需要服务器发送RCPT TO:来告知邮件服务器发送给谁。
    # 因此接收者列表应该是收件人、抄送人、密送人的集合。
    smtp.sendmail(sender, receivers + cc_list + bcc_list, message.as_string())
    smtp.quit()
except smtplib.SMTPException as e:
    print("error: ", e)

案例: 将磁盘使用情况以邮件的形式发送

# coding=utf-8
import smtplib
import subprocess

def send_email(smtp_server, sender, passwd, receiver_list, subject, content):
    receiver = receiver_list
    if isinstance(receiver_list, list):
        receiver = ",".join(receiver_list)  # 多个收件人之间用,隔开

    # 注意主题和正文中有一个空行
    msg = '\r\n'.join([
        'From: %s' % sender,
        'To: %s' % receiver,
        'Subject: %s' % subject,
        '',
        content
    ])

    try:
        s = smtplib.SMTP()
        # 连接smtp服务器
        s.connect(smtp_server)
        # 登陆　对于163邮箱,使用授权码而不是密码登陆第三方邮件客户端
        s.login(sender, passwd)
        # 发送邮件
        s.sendmail(sender, receiver_list, msg)
        print 'success'
        s.quit()
    except Exception as e:
        print e

#　发送邮件测试

def send_email_test():
    smtp_server = 'smtp.163.com'
    sender = 'sender@163.com'  # 发件人
    password = 'authorized_code'  # 163邮箱的登陆授权码

    # 收件人
    receiver = ['qq1@qq.com', 'qq2@qq.com']
    # 邮件主题
    subject = 'Disk Usage Report'

    p = subprocess.Popen('df -h', shell=True, stdout=subprocess.PIPE)
    content = p.stdout.read()  # 获取磁盘使用情况

    send_email(smtp_server, sender, password, receiver, subject, content)

2. 发送富文本邮件

host = "smtp.aliyun.com"
username = "u1@aliyun.com"
password = “password"
receivers = ['q1@qq.com']
subject = "python发送html"

sender = username
# 类型为alternative
message = MIMEMultipart("alternative")
message['From'] = sender
message['To'] = ",".join(receivers)   # 多个接收人之间要用逗号隔开
message['Subject'] = Header(subject, "utf-8")

# 正文有两部分
part1 = MIMEText("<h1>使用python发送邮件</h1>", "html", "utf-8")
part2 = MIMEText('<a href="http://www.python.org">python官网</a>', "html", "utf-8")
message.attach(part1)
message.attach(part2)

3. 发送带附件的邮件

import os
import smtplib
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.header import Header
from email.mime.application import MIMEApplication

def add_attchment(message, file):
    """添加附件
    :param message: MIMEMultipart对象
    :param file: file为文件的路径
    :return: None
    """
    filename = os.path.basename(file)  # 获取文件名
    with open(file, "rb") as f:
        attachment = MIMEApplication(f.read())
        attachment.add_header(
            "Content-Disposition",
            "attachment",
            filename=(
                "gbk",  # 指定编码格式, qq邮箱对邮件使用gbk编码，否则可能会出现文件名乱码
                "",
                filename))
        message.attach(attachment)

host = "smtp.aliyun.com"
username = "u1@aliyun.com"
password = “password"
receivers = ['q1@qq.com']
subject = "python发送附件"

sender = username
# 发送附件，Content-Type必须为multipart/mixed
message = MIMEMultipart("mixed")
message['From'] = sender
message['To'] = ",".join(receivers)   # 多个接收人之间要用逗号隔开
message['Subject'] = Header(subject, "utf-8")
# 添加正文
body = MIMEText("测试发送附件", "html", "utf-8")
message.attach(body)
# 添加附件
add_attchment(message, "百度logo.jpg")
add_attchment(message, "测试.txt")
add_attchment(message, "测试.xlsx")

4. 发送带内嵌图片的邮件

def get_base64name(file):
    """
    :param file: 文件路径
    :return: 返回base64编码的文件名
    """
    filename = os.path.basename(file)
    base64name = base64.b64encode(filename.encode('utf-8'))
    filename = (str(base64name))[2:-1]
    return filename

def add_nested_picture(message, msgalternative, file):
    """
    向邮件中嵌入图片
    """
    # 将base64编码的文件名作为cid
    cid = get_base64name(file)
    link = MIMEText('<img src="cid:%s" />' % cid, "html", "utf-8")
    msgalternative.attach(link)

    with open(file, "rb") as f:
        nested_picture = MIMEApplication(f.read())
        nested_picture.add_header("Content-ID", cid)
       # 下面这一行可以省略
        nested_picture.add_header("Content-Disposition", "inline", filename=("gbk", "", os.path.basename(file)))
        message.attach(nested_picture)

sender = username
# 指定类型为multipart/related
message = MIMEMultipart("related")
message['From'] = sender
message['To'] = ",".join(receivers)   # 多个接收人之间要用逗号隔开
message['Subject'] = Header(subject, "utf-8")
msgalternative = MIMEMultipart("alternative")
message.attach(msgalternative)
# 添加正文
body = MIMEText("测试发送含有内嵌图片的邮件", "html", "utf-8")
msgalternative.attach(body)
add_nested_picture(message, msgalternative, "C:/users/hupeng/pictures/lena.jpg")

层次结果:

里层: 类型为multipart/alternative的MIMEMultipart对象attach 装载html文本的MIMEText对象。

外层: 类型为multipart/related的MIMEMultipart对象 attach 表示内嵌资源的MIMEApplication对象和表示文本信息类型为mulitpart/alternative的MIMEMultipart对象。

当然也可以直接使用类型为multipart/mixed类型的对象attach 表示html文本的MIME对象和表示内嵌资源的MIMEApplication对象

代码如下:

def get_base64name(file):
    """
    :param file: 文件路径
    :return: 返回base64编码的文件名
    """
    filename = os.path.basename(file)
    base64name = base64.b64encode(filename.encode('utf-8'))
    filename = (str(base64name))[2:-1]
    return filename

def add_nested_picture(message, file):
    """
    向邮件中嵌入图片
    """
    # 将base64编码的文件名作为cid
    cid = get_base64name(file)
    link = MIMEText('<img src="cid:%s" />' % cid, "html", "utf-8")
    message.attach(link)

    with open(file, "rb") as f:
        nested_picture = MIMEApplication(f.read())
        nested_picture.add_header("Content-ID", cid)
        message.attach(nested_picture)

sender = username
# 指定最外层信息段类型为multipart/mixed
message = MIMEMultipart("mixed")
message['From'] = sender
message['To'] = ",".join(receivers)   # 多个接收人之间要用逗号隔开
message['Subject'] = Header(subject, "utf-8")
# 添加正文
body = MIMEText("测试发送含有内嵌图片的邮件", "html", "utf-8")
message.attach(body)
# 添加嵌入式图片
add_nested_picture(message, "百度logo.jpg")

备注:  邮件客户端(web端）包含查看邮件原文的功能，使用该功能可以很好的帮助学习。