SMTP

• Simple mail transfer protocol

• port 25

• Telnet - HELO/EHLO

  #install telnet : dism /online /Enable-Feature /FeatureName:TelnetClient

  telnet 10.129.14.128 25

• VRFY

  • can be used once connected by telnet, to confirm the existence of the user

  • vrfy root

• nmap

  • sudo nmap 10.129.14.128 -sC -sV -p25

• Nmap - Open Relay

  • nmap 10.129.14.128 -p25 --script smtp-open-relay -v

nc

nc -nv 192.168.50.8 25

test connection

Test-NetConnection -Port 25 192.168.50.8

username verification

#!/usr/bin/python

import socket
import sys

if len(sys.argv) != 3:
        print("Usage: vrfy.py <username> <target_ip>")
        sys.exit(0)

# Create a Socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Connect to the Server
ip = sys.argv[2]
connect = s.connect((ip,25))

# Receive the banner
banner = s.recv(1024)

print(banner)

# VRFY a user
user = (sys.argv[1]).encode()
s.send(b'VRFY ' + user + b'\r\n')
result = s.recv(1024)

print(result)

# Close the socket
s.close()

save above code to smtp.py then run

python3 smtp.py <username> <IP>