> For the complete documentation index, see [llms.txt](https://docs.h4rithd.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.h4rithd.com/tcp/25-smtp.md). # SMTP | 25, 587

Command	Description
HELO	Introduces the client to the server (used in SMTP).
EHLO	Extended HELO; used in ESMTP to request server capabilities.
MAIL FROM:	Specifies the sender's email address.
RCPT TO:	Specifies the recipient's email address.
DATA	Indicates that the email content (headers + body) follows.
RSET	Resets the current mail transaction.
VRFY	Verifies if a user/email address exists on the server.
EXPN	Expands a mailing list to show all recipients.
NOOP	No operation; used to keep the connection alive.
QUIT	Terminates the SMTP session.
STARTTLS	Initiates a TLS-secured connection (if supported).
AUTH	Begins the authentication process (e.g, LOGIN, PLAIN, CRAM-MD5).

Code	Type	Meaning
211	Success	System status or help reply
214	Success	Help message
220	Success	Service ready
221	Success	Service closing transmission channel
250	Success	Requested action completed
251	Success	User not local; will forward
252	Success	Cannot verify user, but will accept message
354	Intermediate	Start mail input; end with .
421	Error	Service not available, closing transmission channel
450	Error	Requested action not taken: mailbox unavailable
451	Error	Requested action aborted: local error in processing
452	Error	Requested action not taken: insufficient system storage
500	Error	Syntax error, command unrecognized
501	Error	Syntax error in parameters or arguments
502	Error	Command not implemented
503	Error	Bad sequence of commands
504	Error	Command parameter not implemented
550	Error	Requested action not taken: mailbox unavailable
551	Error	User not local; please try
552	Error	Requested mail action aborted: exceeded storage allocation
553	Error	Requested action not taken: mailbox name not allowed
554	Error	Transaction failed (message rejected)

* Nmap Script ```bash sudo nmap --script smtp-enum-users -p25 sudo nmap --script smtp-open-relay,smtp-commands,smtp-ntlm-info -p25 ``` * Username enumerate ```bash ## ------------------| smtp-user-enum smtp-user-enum -M VRFY -U /usr/share/seclists/Usernames/Names/names.txt -t 10.10.10.17 smtp-user-enum -U /usr/share/seclists/Usernames/Honeypot-Captures/multiplesources-users-fabian-fingerle.de.txt -m 50 -M RCPT -D humongousretail.com -t 10.10.10.17 ## ------------------| Metasploit msfconsole use auxiliary/scanner/smtp/smtp_enum set RHOSTS $IP set USER_FILE /usr/share/seclists/Usernames/Names/names.txt set THREADS 10 set RPORT 25 run ## ------------------| Bash Script for i in $(cat /usr/share/seclists/Usernames/Names/names.txt);do echo -e "HELO test.com\nVRFY $i\nQUIT" | nc -nv $IP 25 | grep -E "250|550"; done ``` * Check Auth ```bash telnet 587 EHLO mailserver.com AUTH LOGIN # echo -n "username" | base64 # echo -n "password" | base64 ``` * Send mail

## !! Be aware about from address. If you are using same domain for both from and to. they will ask auth. So please use info@h4rithd.com first !!
## ------------------| Using Swaks
swaks --from info@h4rithd.com --to admin@sneakymailer.htb --header 'Subject: Hello world' --body 'This is msg body' --server 10.10.10.197
    
## ------------------| Using sendEmail
sendEmail -m 'Hello machan' -f info@h4rithd.com  -t admin@sneakymailer.htb -s <IP> -u "Message Subject" -a attachment.pdf                            
sendEmail -o message-file=message.txt -f info@h4rithd.com  -t admin@sneakymailer.htb -s <IP> -u "Message Subject" -a attachment.pdf                            

## ------------------| Using Telnet
telnet <IP> 25
HELO writer.htb
MAIL FROM:info@h4rithd.com
RCPT TO:root@writer.htb
DATA
Subject: Test mail
Hello h4rith
.
QUIT

## ------------------| Using NetCat  
nc <IP> 25
HELO writer.htb
MAIL FROM:info@h4rithd.com
RCPT TO:root@writer.htb
DATA
Subject: Test mail
Hello h4rith
.
QUIT

## ------------------| Using NodeJS
const nodemailer = require('nodemailer');

const transporter = nodemailer.createTransport({
  host: 'smtp.example.com',       // Your provider's SMTP server
  port: 587,                      // Common: 587 (STARTTLS), 465 (SSL), 25 (non-auth, old)
  secure: false,                  // true for 465, false for other ports
  auth: {
    user: 'your@email.com',       // Your email address
    pass: 'your_password_or_app_password'
  }
});

// Optional: For self-signed certs or debugging
// tls: {
//   rejectUnauthorized: false
// }

const mailOptions = {
  from: '"HarithD" <hello@h4rithd.com>',
  to: 'recipient@h4ritd.com',
  subject: 'SMTP Test',
  text: 'Test email',
  // html: '<p>HTML body with <strong>custom SMTP</strong></p>'
};

transporter.sendMail(mailOptions, (error, info) => {
  if (error) {
    return console.error('Send error:', error);
  }
  console.log('Email sent:', info.response);
});

* SMTP server ```python ## ------------------| Using smtpd (deprecated) import smtpd import asyncore class CustomSMTPServer(smtpd.SMTPServer): def __init__(self, localaddr, remoteaddr): smtpd.SMTPServer.__init__(self, localaddr, remoteaddr) def process_message(self, peer, mailfrom, rcpttos, data): print('Received email from:', mailfrom) print('To:', rcpttos) print('Message:', data) server = CustomSMTPServer(('0.0.0.0', 1025), None) asyncore.loop() ## ------------------| Using asyncio import asyncio from aiosmtpd.controller import Controller class CustomSMTPHandler: async def handle_RCPT(self, server, session, envelope, address, rcpt_options): envelope.rcpt_tos.append(address) return '250 OK' async def handle_DATA(self, server, session, envelope): print('Received email from:', envelope.mail_from) print('To:', envelope.rcpt_tos) print('Message:', envelope.content.decode('utf-8')) return '250 OK' async def main(loop): handler = CustomSMTPHandler() controller = Controller(handler, hostname='localhost', port=1025) controller.start() loop = asyncio.get_event_loop() loop.run_until_complete(main(loop)) ```