SMTP

首先我们用命令行的方式去发送一封邮件，步骤为：

1. 使用telnet连接发送方邮箱服务器
2. 跟发送方邮箱服务器进行第一次交流（打招呼）
3. 验证登录（需要密码和激活码）
4. 填写发送方接收方信息
5. 填写正文信息
6. 发送

telnet smtp.163.com 25
220 163.com Anti-spam GT for Coremail System (163com[20141201])
helo smtp
250 OK
auth login
334 dXNlcm5hbWU6
（填写经过base64编码之后的发送方邮箱地址）
334 UGFzc3dvcmQ6
（填写经过base64编码之后的激活码）
235 Authentication successful
mail from:<zhangchengming23j@163.com>
250 Mail OK
rcpt to:<2419792150@qq.com>
250 Mail OK
data
354 End data with .
subject:testmail

test successful ok!
.
250 Mail OK queued as smtp14,EsCowABnTd7Jvedh70gXBA–.42727S3 1642577594

接着就可以在qq邮箱中受到邮件了

注：smtp协议命令行发送邮件格式
helo smtp：打招呼
auth login：验证登录，这里的输入需要base64进行编码
mail from:<你的发件邮箱>
rcpt to:<接收邮箱>
data
subject:填写邮件主题
<空一行>
填写邮件内容
…
邮件内容
.

题目要求
1.创建一个邮件用户代理，可以向任何接收方发送电子邮件
2.该用户代理与邮件的服务器创建TCP连接
3.使用SMTP协议与服务器交谈
4.用该邮件用户代理向一个邮箱发送一封邮件，最后关闭该TCP连接

S1 创建和客户端服务器相连的客户端socket

clientSocket = socket(AF_INET, SOCK_STREAM)

recv = clientSocket.recv(1024).decode()

s2:该用户代理与邮件的服务器创建TCP连接

# 创建客户端socket（socketClient），和接收方邮箱服务器进行第一次连接
clientSocket = socket(AF_INET, SOCK_STREAM)  # 创建一个客户端socket
connect_smtp = False
while connect_smtp == False:try:clientSocket.connect((mailServer, 25))  # 客户端的socket和接收方邮件服务器相连接，并进行第一次交流print('-> Creat TCP cnnnection with SMTP server:{}\r\n'.format(mailServer))  # 当上一步连接成功之后格式化输出该字符串# clientSocket使用recv方法从接收方邮箱服务器接收数据，这里规定最大接收1024字节的数据，并使用.decode进行编码# 此时是客户端socket和接受方邮箱服务器第一次“握手？” 正常情况接收方邮箱服务器返回 220....给客户端socketrecv = clientSocket.recv(1024).decode()print('<- ' + recv)if recv[:3] != '220':print('! 220 reply not received from Server.\r\n')connect_smtp = Trueexcept:print('! Your SMTP server or network connection is unavailable.\r\n')mailServer = input('Please reenter your SMTP server address:')print('\r\n')# 和接收方邮箱服务器进行第二次交流heloCommand = 'HELO TestProgram\r\n'
clientSocket.send(heloCommand.encode())  # 将'HELO TestProgram\r\n'进行编码，使用send方法将该数据发送给接收方邮箱服务器
print('->' + heloCommand)
# 当使用send方法将该数据发送给接收方邮箱服务器后，接收方邮箱服务器会返回响应数据给发送方socket，recv1用来接收该数据
recv1 = clientSocket.recv(1024).decode()
print('<-' + recv1)
if recv1[:3] != '250':print('! 250 reply not received from server.\r\n')

s3:使用SMTP协议与服务器交谈

# 完成auth login 步骤
login = False
while not login:clientSocket.send('AUTH LOGIN\r\n'.encode())print('->AUTH LOGIN\r\n')recv2 = clientSocket.recv(1024).decode()recv2de = recv2[:4] + base64.b64decode(recv2[4:]).decode()print('<-' + recv2de + '\r\n')if recv2[:3] != '334':print('! 334 reply not received from server.\r\n')fromadd_encode = base64.b64encode(fromAdd.encode()) + '\r\n'.encode()clientSocket.send(fromadd_encode)print('-> Send base64 encrypted username\r\n')recv3 = clientSocket.recv(1024).decode()recv3de = recv3[:4] + base64.b64decode(recv3[4:]).decode()print('<- ' + recv3de + '\r\n')if recv3[:3] != '334':print('!  334 reply not received from server.\r\n')fromPass_encode = base64.b64encode(fromPass.encode()) + '\r\n'.encode()clientSocket.send(fromPass_encode)print('-> Send base64 encrypted password\r\n')recv4 = clientSocket.recv(1024).decode()print('<- ' + recv4)if recv4[:3] != '235':print('!  235 reply not received from server.\r\n')fromAdd = input('Please reenter your mailbox address: ')fromPass = input('Please reenter your mailbox password: ')print('\r\n')else:login = True# 编写mail from:<>
# 接收并判断返回信息
mailFromCommand = 'mail from:<{}>\r\n'.format(fromAdd)
clientSocket.send(mailFromCommand.encode())
print('->' + mailFromCommand)
recv5 = clientSocket.recv(1024).decode()
print('<-' + recv5)
if recv5[:3] != '250':print('! 250reply not received from server.\r\n')# 编写rcpt to:<>
rcpttoCommand = 'RCPT TO:<{}>\r\n'.format(toAdd)
clientSocket.send(rcpttoCommand.encode())
print('->' + rcpttoCommand)
recv6 = clientSocket.recv(1024).decode()
print('<- ' + recv6)
if recv6[:3] != '250':print('! 250 reply not received from server.\r\n')dataToCommand = 'DATA\r\n'
clientSocket.send(dataToCommand.encode())
print('->' + dataToCommand)
recv7 = clientSocket.recv(1024).decode()
print('<-' + recv7)
if recv7[:3] != '354':print('! 354 reply not received from server.\r\n')

s4:用该邮件用户代理向一个邮箱发送一封邮件，最后关闭该TCP连接

# 发送msg
msg = '''From: "TestMailbox" <{}>
To: "TestReport" <{}>
Subject: A test mail from SMTP mail test system
Content-Type: text/plain;This is a test mail from SMTP mail test system v0.1.
Your mailbox {} is working.
'''.format(fromAdd, toAdd, fromAdd)
clientSocket.send(msg.encode())
clientSocket.send(endMsg.encode())
print('->' + msg)
recv8 = clientSocket.recv(1024).decode()
print('<-' + recv8)
if recv8[:3] != '250':print('! 250 reply not received from server.\r\n')