Individual skill
pentesting-smtp
Testing SMTP services (default ports 25, 465/SSL, 587/submission) for open relays, user enumeration (VRFY/EXPN/RCPT), NTLM info disclosure, weak/no authentication, SPF/DKIM/DMARC spoofing gaps, Secure Email Gateway bypass, and SMTP smuggling during authorized engagements.
internal/tools/skills/data/network-services-pentesting/pentesting-smtp/SKILL.md
Source commit d42f381ad34843e71a42658e5c57290c713e85af
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- Skill scan complete
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- Observed behavior
- Not checked yet
- Last checked
- Nov 7, 2026
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Repository context
- Repository stars (not skill ratings)
- 1,312
- Repository last updated
- Nov 7, 2026
- License
- Apache-2.0
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- cybersecurity Repository topic
- security Repository topic
- bug-bounty Repository topic
- automation Repository topic
- autonomous-pentesting Repository topic
- ai-agent Repository topic
- ai-security Repository topic
- ethical-hacking Repository topic
- golang Repository topic
- penetration-testing Repository topic
- penetration-testing Declared skill tag
- network-services Declared skill tag
- smtp Declared skill tag
- security Derived category
- testing Derived category
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# Pentesting SMTP (ports 25, 465, 587)
## When to Use
- Default ports: `25/tcp` (MTA-to-MTA), `465/tcp` (SMTPS), `587/tcp` (submission/STARTTLS).
- When `nmap`/banner shows `smtp`, `ESMTP`, `Sendmail`, `Postfix`, `Exim`, or `Microsoft ESMTP`.
- For testing relay policy, user enumeration, email-spoofing controls (SPF/DKIM/DMARC), and gateway routing.
## Quick Enumeration
```bash
# Plaintext banner + manual session
nc -vn <IP> 25
# SMTPS / STARTTLS
openssl s_client -crlf -connect <IP>:465 # implicit TLS