smtp-penetration-testing — Claude Code skill
A Claude skill that walks the agent through SMTP checks: banner grabbing, user enumeration, open relay tests, credential brute force.
npx claude-code-templates@latest --skill security/smtp-penetration-testingWhat smtp-penetration-testing does
The skill splits SMTP work into ten phases. The agent starts with architecture and ports, discovers the service with nmap, reads the banner, probes VRFY, EXPN and RCPT TO, tests for an open relay, tries credentials, then inspects TLS. Header injection and SPF, DKIM, DMARC lookups get their own phases.
Each step ships with commands to run: nmap --script smtp-*, smtp-user-enum, hydra, medusa, Metasploit modules, and openssl s_client with -starttls smtp. Deliverables are a findings report, the list of addresses that turned out valid, relay status, and hardening notes.
Skip the tool install and half the phases go nowhere — nmap, netcat, hydra, smtp-user-enum and Metasploit have to be on the box. You also need a target, wordlists, and written authorization. Running this against a server you do not own or have a signed scope for is on you.
What it helps with
- grab the SMTP banner and identify the mail software
- enumerate valid addresses with VRFY, EXPN and RCPT TO
- check whether the server relays mail for outsiders
- brute force weak SMTP authentication credentials
- inspect STARTTLS support and the cipher list
Example prompts for the agent
- Run an SMTP audit against
mail.example.com: grab the banner and list the supported extensions - Enumerate users on this SMTP server with
smtp-user-enumand theusers.txtwordlist - Test whether this server is an open relay and show me the result
How to install smtp-penetration-testing
1claude-code-templates
npx claude-code-templates@latest --skill security/smtp-penetration-testing2Skills CLI (Vercel)
npx skills add davila7/claude-code-templates --skill smtp-penetration-testing -a claude-code3Manually: put the files in place
~/.claude/skills/smtp-penetration-testing/SKILL.mdCopy the whole skill folder; for one project use .claude/skills/smtp-penetration-testing/
Manually: put the files in place
.agents/skills/smtp-penetration-testing/SKILL.mdFor all projects use ~/.agents/skills/
Manually: put the files in place
.cursor/skills/smtp-penetration-testing/SKILL.mdCursor also reads .agents/skills/ and .claude/skills/
1GitHub CLI
gh skill install davila7/claude-code-templates smtp-penetration-testing2Manually: put the files in place
.github/skills/smtp-penetration-testing/SKILL.mdPlatform CLI
gemini skills install https://github.com/davila7/claude-code-templates --path cli-tool/components/skills/security/smtp-penetration-testingManually: put the files in place
.devin/skills/smtp-penetration-testing/SKILL.mdThe legacy .windsurf/skills/ path still works
Claude.ai
Zip the folder and upload it in Settings → Capabilities → Skills
Step by step, with commands for each platform: How to install skills in Claude Code: five ways
Questions about smtp-penetration-testing
How do I install smtp-penetration-testing in Claude Code?
Use the templates CLI: npx claude-code-templates@latest --skill security/smtp-penetration-testing. Or add it with npx skills add davila7/claude-code-templates --skill smtp-penetration-testing -a claude-code. The skill file lands at ~/.claude/skills/smtp-penetration-testing/SKILL.md.
What does smtp-penetration-testing do?
It runs an SMTP assessment in phases: service discovery, banner grabbing, user enumeration, open relay testing, credential brute force, header injection, TLS checks, and email authentication records. The agent then writes up the findings with hardening guidance.
What do I need before running it?
nmap, netcat, hydra, smtp-user-enum and Metasploit installed, a target address, wordlists for enumeration and brute force, and written authorization for the test.
