Python SMTP：发送电子邮件的简便方法

一、什么是SMTP

SMTP 是 Simple Mail Transfer Protocol（简单邮件传输协议）的缩写，是用于发送邮件的协议。Python 提供了 smtplib 模块，它对 SMTP 协议进行了封装，可以很方便地发送邮件。

二、SMTP的原理

SMTP 协议是基于文本的，它的每条命令都是一行文本，以 CR-LF（回车和换行）结尾。在 Python 中，可以使用 smtplib 模块的 SMTP 类来创建一个 SMTP 连接，然后发送邮件。

import smtplib
from email.mime.text import MIMEText

mail_host = "smtp.163.com"        # 邮箱服务器地址
mail_user = "your_email_address"  # 邮箱账号
mail_pass = "your_email_password" # 邮箱密码

sender = "your_email_address"     # 发件人邮箱
receiver = "receiver_email_address" # 收件人邮箱列表

# 邮件内容
msg = MIMEText("邮件内容")
msg['Subject'] = "邮件主题"
msg['from'] = sender
msg['to'] = ','.join(receiver)

# 创建一个 SMTP 连接
smtpObj = smtplib.SMTP()
smtpObj.connect(mail_host, 25)
smtpObj.login(mail_user, mail_pass)

# 发送邮件
smtpObj.sendmail(sender, receiver, msg.as_string())
smtpObj.quit()

三、使用SMTP发送携带附件的邮件

在有些情况下，我们需要发送携带附件的邮件。可以使用 email.mime.multipart 模块的 MIMEMultipart 类来组合邮件内容，并添加附件。

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

mail_host = "smtp.163.com"        # 邮箱服务器地址
mail_user = "your_email_address"  # 邮箱账号
mail_pass = "your_email_password" # 邮箱密码

sender = "your_email_address"     # 发件人邮箱
receiver = "receiver_email_address" # 收件人邮箱列表

# 组合邮件内容
msg = MIMEMultipart()
msg['Subject'] = "邮件主题"
msg['from'] = sender
msg['to'] = ','.join(receiver)

# 添加文本内容
body = "邮件正文"
msg.attach(MIMEText(body, 'plain', 'utf-8'))

# 添加附件
filename = "test.txt"
part = MIMEApplication(open(filename,'rb').read(), Name=filename)
part['Content-Disposition'] = 'attachment; filename="%s"' % filename
msg.attach(part)

# 创建一个 SMTP 连接
smtpObj = smtplib.SMTP()
smtpObj.connect(mail_host, 25)
smtpObj.login(mail_user, mail_pass)

# 发送邮件
smtpObj.sendmail(sender, receiver, msg.as_string())
smtpObj.quit()

四、使用SMTP发送HTML格式邮件

有时候我们需要发送 HTML 格式的邮件，可以使用 email.mime.text 模块的 MIMEText 类来设置 HTML 格式的邮件内容。

import smtplib
from email.mime.text import MIMEText

mail_host = "smtp.163.com"        # 邮箱服务器地址
mail_user = "your_email_address"  # 邮箱账号
mail_pass = "your_email_password" # 邮箱密码

sender = "your_email_address"     # 发件人邮箱
receiver = "receiver_email_address" # 收件人邮箱列表

# 邮件内容
msg = MIMEText("
这是一封 HTML 格式的电子邮件
百度", "html", "utf-8")
msg['Subject'] = "邮件主题"
msg['from'] = sender
msg['to'] = ','.join(receiver)

# 创建一个 SMTP 连接
smtpObj = smtplib.SMTP()
smtpObj.connect(mail_host, 25)
smtpObj.login(mail_user, mail_pass)

# 发送邮件
smtpObj.sendmail(sender, receiver, msg.as_string())
smtpObj.quit()

五、SMTP发送带图片的邮件

如果我们需要在邮件中插入图片，可以使用 email.mime.multipart 模块的 MIMEMultipart 类来组合邮件内容并添加图片。

import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.image import MIMEImage

mail_host = "smtp.163.com"        # 邮箱服务器地址
mail_user = "your_email_address"  # 邮箱账号
mail_pass = "your_email_password" # 邮箱密码

sender = "your_email_address"     # 发件人邮箱
receiver = "receiver_email_address" # 收件人邮箱列表

# 组合邮件内容
msg = MIMEMultipart()
msg['Subject'] = "邮件主题"
msg['from'] = sender
msg['to'] = ','.join(receiver)

# 添加HTML内容
html = "
这是一封包含图片的邮件
"
msg.attach(MIMEText(html, "html", "utf-8"))

# 添加图片
fp = open('test.png', 'rb')
msgImage = MIMEImage(fp.read())
fp.close()

msgImage.add_header('Content-ID', '')
msg.attach(msgImage)

# 创建一个 SMTP 连接
smtpObj = smtplib.SMTP()
smtpObj.connect(mail_host, 25)
smtpObj.login(mail_user, mail_pass)

# 发送邮件
smtpObj.sendmail(sender, receiver, msg.as_string())
smtpObj.quit()

通过使用 Python 的 smtplib 模块，我们可以很方便地发送各种邮件，不管是纯文本邮件还是携带附件或图片的复杂邮件。同时，由于 Python 自带的简单写法和常用库的支持，使得大多数功能都能用少量代码来实现。