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Postfix

Postfix is a free, open source mail transfer agent (MTA) originally written by Wietse Venema at IBM Research as a fast, secure, and easy-to-administer alternative to Sendmail. It runs on UNIX-like systems including Linux, BSD, and macOS, routing and delivering email over SMTP with extensive support for TLS, SASL, DKIM/SPF/DMARC integration, content filtering, and policy delegation. Postfix is administered via configuration files (main.cf, master.cf) and command-line tools rather than a public HTTP API, and is one of the most widely deployed mail servers on the internet.

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EmailMail ServerMTASMTPOpen SourceInfrastructure

APIs

Postfix SMTP

Postfix implements SMTP (RFC 5321) for sending and receiving electronic mail, with submission (port 587), SMTPS (port 465), and standard SMTP (port 25) endpoints. There is no pu...

Resources

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Website
Website
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Documentation
Documentation
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Download
Download
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Source Code
Source Code
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Mailing Lists
Mailing Lists
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Security
Security
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License
License
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Wikipedia
Wikipedia

Sources

apis.yml Raw ↑ 
aid: postfix
name: Postfix
description: >-
  Postfix is a free, open source mail transfer agent (MTA) originally written
  by Wietse Venema at IBM Research as a fast, secure, and easy-to-administer
  alternative to Sendmail. It runs on UNIX-like systems including Linux, BSD,
  and macOS, routing and delivering email over SMTP with extensive support for
  TLS, SASL, DKIM/SPF/DMARC integration, content filtering, and policy
  delegation. Postfix is administered via configuration files (main.cf,
  master.cf) and command-line tools rather than a public HTTP API, and is one
  of the most widely deployed mail servers on the internet.
type: Index
image: https://kinlane-productions.s3.amazonaws.com/apis-json/apis-json-logo.jpg
tags:
  - Email
  - Mail Server
  - MTA
  - SMTP
  - Open Source
  - Infrastructure
url: >-
  https://raw.githubusercontent.com/api-evangelist/postfix/refs/heads/main/apis.yml
created: '2026-05-11'
modified: '2026-05-11'
specificationVersion: '0.19'
apis:
  - aid: postfix:smtp
    name: Postfix SMTP
    description: >-
      Postfix implements SMTP (RFC 5321) for sending and receiving electronic
      mail, with submission (port 587), SMTPS (port 465), and standard SMTP
      (port 25) endpoints. There is no public HTTP/REST API; integration is
      via SMTP protocol, configuration files, milter (mail filter) hooks, and
      policy daemons.
    humanURL: https://www.postfix.org/documentation.html
    baseURL: smtp://localhost:25
    tags:
      - SMTP
      - Email
      - Mail Server
      - Protocol
    properties:
      - type: Documentation
        url: https://www.postfix.org/documentation.html
      - type: SMTP Specification
        url: https://datatracker.ietf.org/doc/html/rfc5321
      - type: Configuration Reference
        url: https://www.postfix.org/postconf.5.html
      - type: Milter Protocol
        url: https://www.postfix.org/MILTER_README.html

common:
  - type: Website
    url: https://www.postfix.org
  - type: Documentation
    url: https://www.postfix.org/documentation.html
  - type: Download
    url: https://www.postfix.org/download.html
  - type: Source Code
    url: https://github.com/vdukhovni/postfix
  - type: Mailing Lists
    url: https://www.postfix.org/lists.html
  - type: Security
    url: https://www.postfix.org/security.html
  - type: License
    url: https://www.postfix.org/license.html
  - type: Wikipedia
    url: https://en.wikipedia.org/wiki/Postfix_(software)
maintainers:
  - FN: Kin Lane
    email: [email protected]