ismtp

SMTP user enumeration and testing tool

uncategorizedRed Team

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Platforms: Linux · Last verified September 6, 2026

Test for SMTP user enumeration (RCPT TO and VRFY), internal spoofing, and relay.

Only use this tool against systems you own or are explicitly authorized to test — see the disclaimer.

Getting started

Install on Kali Linux with `sudo apt install ismtp`. See the official Kali tool page and upstream homepage linked above for full usage and configuration details.

Commonly preinstalled on

Kali Linux

Debian-based distribution built for penetration testing and security auditing