# emersion/go-smtp

📤 An SMTP library for Go clients and servers

Repository: https://github.com/emersion/go-smtp
Canonical: https://ross.abutalabs.com/products/go-smtp
Language: Go
License: MIT
License Family: permissive
Topics: mail, server, client, smtp, esmtp, lmtp
Last push: 2026-08-18T08:01:46+00:00

## Health v2 (maintenance only)
Score: 94/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 98, release rhythm 85, longevity 100
- inputs: {"age_days": 3696, "days_push": 15, "days_rel": 20, "gap_med": 62, "n_releases_24m": 4}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2042, forks 270 (observed 2026-08-28T04:06:08.531919+00:00)

## What it is
An ESMTP client and server library for Go implementing RFC 5321 with extensions like AUTH, PIPELINING, and LMTP. It improves on the frozen net/smtp standard library package by adding server support and client enhancements.

## Use cases
- send email from a Go application
- build an SMTP server in Go
- implement LMTP for a mail server
- add SMTP AUTH support to a mail client
- replace net/smtp with a maintained library
- receive and parse incoming mail in Go

## When to choose
- you need both SMTP client and server functionality in Go
- you need SMTP extensions like AUTH, PIPELINING, or LMTP
- you want an actively maintained alternative to net/smtp

## When to avoid
- you only need basic SMTP sending and net/smtp suffices
- you need a full mail transfer agent rather than a library
- you are not working in Go

## Facets
- artifact type: library
- maturity: active
- function: email, http-server, auth
- domain: email, backend, developer-tools
- platform: go, cross-platform
- tags: smtp, esmtp, lmtp, mail-server, mail-client, rfc5321

## Member repositories
- emersion/go-smtp (main) score 94

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:08.531919+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 2026-08-30T02:58:17.695793+00:00, confidence not recorded.
  - readme: https://github.com/emersion/go-smtp (fetched 2026-08-28T04:06:08.531919+00:00, sha 3847e8393213)
- Data as of 2026-08-30T08:39:29.467469+00:00.