SMTP Enumeration

Simple Mail Transfer Protocol has VRFY request asks the server to verify an email address, while EXPN asks the server for the membership of a mailing list. PORT 25

• Manual

  • nc -nv <ip> 25

  • VRFY <user> if user not exist in mail server , it give error

• Automated script

  🐍

  #!/usr/bin/python

  import socket
  import sys
  

  if len(sys.argv) != 3:
  print(f"Usage: {sys.argv[0]} <ip_address> <username_file>")
  sys.exit(0)
  

  #Read the IP address and file name from the command line arguments

  ip_address = sys.argv[1]
  filename = sys.argv[2]
  

  #Read usernames from the text file

  try:
  with open(filename, "r") as f:
  usernames = f.read().splitlines()
  except IOError:
  print(f"Error: Unable to read from file '{filename}'")
  sys.exit(1)
  

  #Create a Socket

  s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

  #Connect to the Server

  connect = s.connect((ip_address, 25))

  #Receive the banner

  banner = s.recv(1024)

  print(banner)

  #Loop through each username and VRFY

  for username in usernames:
  s.send(f'VRFY {username}\r\n')
  result = s.recv(1024)
  

  print(result)

  #Close the socket
  s.close()
  

• Send Mail on SMTP

  • telnet <ip> 25

  • Set sender’s email
    MAIL FROM: sender@adress.ext
    

  • Set recipient mail
    RCPT TO: recipient@adress.ext
    

  • To write the message, type DATA and press ‘Enter’
    
    DATA

  • On the first line type ‘SUBJECT: Your Subject’ and press ‘Enter’ twice
    
    SUBJECT: Your Subject

  • Continue typing your message like
    
    Hello,
    this is test message
    

  • Put a single period (.) on a line by itself and press ‘Enter’ to send your message.
    
    .

  • Close the connection
    
    QUIT

  
  Reference:
  https://www.shellhacks.com/send-email-smtp-server-command-line/