# lettre/lettre

a mailer library for Rust

Repository: https://github.com/lettre/lettre
Canonical: https://ross.abutalabs.com/products/lettre
Homepage: https://lettre.rs
Language: Rust
License: MIT
License Family: permissive
Topics: rust, email, smtp, mailer, sendmail, mailer-library, hacktoberfest
Last push: 2026-08-03T11:10:09+00:00

## Health v2 (maintenance only)
Score: 92/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 95, release rhythm 84, longevity 100
- inputs: {"age_days": 4594, "days_push": 30, "days_rel": 30, "gap_med": 40, "n_releases_24m": 16}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2255, forks 233 (observed 2026-08-28T04:06:31.283446+00:00)

## What it is
lettre is a mailer library for Rust that lets applications compose and send emails via SMTP, sendmail, and other transports. It offers a strongly typed email builder with MIME support, secure SMTP delivery with authentication and encryption, Unicode/internationalized addresses, and async support.

## Use cases
- send emails from a Rust application
- send transactional email via SMTP with authentication
- build emails with attachments and embedded images in Rust
- send email asynchronously from a web backend
- send mail through a local sendmail command
- send password reset or notification emails from a Rust service

## When to choose
- you need to send (not parse or receive) email from Rust code
- you want a typed, safe email builder with MIME, attachments, and Unicode support
- you need secure SMTP delivery with TLS and credentials out of the box
- you want async email sending in a Rust web service

## When to avoid
- you need to parse, read, or receive incoming emails
- you need a full email client with mailbox management (IMAP, folders)
- your project must support Rust versions older than 1.74

## Facets
- artifact type: library
- maturity: stable
- function: email, http-client
- domain: email, backend, developer-tools
- platform: rust, cross-platform
- tags: smtp, mailer, sendmail, email-builder, async

## Member repositories
- lettre/lettre (main) score 92

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:31.283446+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 2026-08-30T02:43:45.322078+00:00, confidence not recorded.
  - readme: https://github.com/lettre/lettre (fetched 2026-08-28T04:06:31.283446+00:00, sha 70db5c1c519c)
  - homepage: https://lettre.rs (fetched 2026-08-29T10:23:42.839700+00:00, sha 9f6b3c45c858)
  - registry_crates: https://crates.io/api/v1/crates/lettre (fetched 2026-08-29T10:23:42.842571+00:00, sha 16ddad7e12ef)
- Data as of 2026-08-30T08:39:29.467469+00:00.