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For the complete documentation index, see llms.txt. This page is also available as Markdown.

SMTP

Simple Mail Transfer Protocol

Check if sender could be forged with an domain user:

$ telnet mail.example.com 25
HELO example.com
MAIL FROM: <forged@example.com>
RCPT TO: <exists@example.com>
RCPT TO: <exists@gmail.com>

Check if sender could be forged with a non-domain user:

$ telnet mail.example.com 25
HELO example.com
MAIL FROM: <forged@gmail.com>
RCPT TO: <exists@example.com>
RCPT TO: <exists@gmail.com>

Check if domain users could be enumerated with VRFY and EXPN:

$ telnet mail.example.com 25
HELO example.com
VRFY exists@example.com
EXPN exists@example.com

Check if users could be enumerated with RCPT TO:

$ telnet mail.example.com 25
HELO example.com
MAIL FROM: <...>
RCPT TO: <exists@example.com>
DATA
From: <...>
To: <exists@example.com>
Subject: Job offer
Hello, I would like to offer you a great job!
.
QUIT

RCPT

smtp-enum

smtp-user-enum

SPF/DKIM/DMARC

Tools

swaks

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