# rnwood/smtp4dev

smtp4dev - the fake smtp email server for development and testing

Repository: https://github.com/rnwood/smtp4dev
Canonical: https://ross.abutalabs.com/products/smtp4dev
Language: C#
License: BSD-3-Clause
License Family: permissive
Topics: smtp4dev, smtp-server, linux, windows, macosx
Last push: 2026-08-25T13:01:36+00:00

## Health v2 (maintenance only)
Score: 90/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 73, longevity 100
- inputs: {"age_days": 5346, "days_push": 8, "days_rel": 183, "gap_med": 4.5, "n_releases_24m": 19}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3945, forks 423 (observed 2026-08-28T04:08:30.267004+00:00)

## What it is
smtp4dev is a fake SMTP email server for development and testing, with a web interface, terminal UI, and REST API. It captures outgoing mail from applications so developers can inspect messages without emailing real recipients.

## Use cases
- test email sending locally without spamming real users
- inspect HTML email rendering and compatibility
- capture SMTP traffic during integration tests
- retrieve test emails via IMAP or POP3
- simulate SMTP errors and TLS scenarios
- run a disposable mail server in Docker for CI

## When to choose
- you need a full-featured local SMTP catch-all with a web UI
- you want IMAP/POP3 access, multiple mailboxes, or relay rules in a dev mail server
- you need cross-platform or Docker-based email testing

## When to avoid
- you need a production mail transfer agent or real mail delivery
- you only need a minimal catch-all with no UI and prefer a tiny daemon
- your stack cannot run .NET

## Facets
- artifact type: application
- maturity: active
- function: http-server, email, testing, developer-tools, gui, terminal-ui
- domain: developer-tools, email, testing, self-hosted
- platform: windows, cross-platform, self-hosted
- tags: smtp-server, fake-smtp, email-testing, imap, pop3, mail-server, dotnet, web-interface, linux, macos, docker

## Member repositories
- rnwood/smtp4dev (main) score 90

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:30.267004+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:24:35.283604+00:00, confidence not recorded.
  - readme: https://github.com/rnwood/smtp4dev (fetched 2026-08-28T04:08:30.267004+00:00, sha 3f1cd5ec142c)
- Data as of 2026-08-30T08:39:29.467469+00:00.