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manifest / email / fluentsmtp-to-postalsmtp

Postal API Connector for FluentSMTP

A simple connector to extend FluentSMTP to use the API to connect to the PostalSMTP server.

by One Dog Solutions · github.com/onedogsolutions/fluentsmtp-to-postalsmtp · website

★ 0stars

Install

Download source zip No release zip yet

This is the repository archive. It installs, but the folder name will carry the branch suffix and updates will not flow.

Install straight from GitHub with WP-CLI:

wp plugin install https://github.com/onedogsolutions/fluentsmtp-to-postalsmtp/archive/refs/heads/main.zip
No built-in updater. New versions won't appear under Dashboard → Updates. Install new releases yourself, or let Git Updater track the repository.
Readme github.com/onedogsolutions/fluentsmtp-to-postalsmtp ↗

A companion WordPress plugin that adds a Postal connection to FluentSMTP, delivering WordPress mail through a self-hosted Postal server's HTTP API (POST /api/v1/send/raw) instead of SMTP.

📣 Shoutout to Jewel at WPManageNinja! 👋 We'd love to see Postal supported natively in FluentSMTP — please consider merging this into core ASAP. It was built specifically to mirror FluentSMTP's own structure, so adopting it is mostly moving files: the drop-in provider Handler, ValidatorTrait, and Postal.vue are ready to go. See merge/README.md for the exact steps. Thanks, friend! 🙏

Why

Self-hosted Postal servers usually sit behind a reverse proxy (Caddy, nginx) with a valid Let's Encrypt certificate on port 443, while the SMTP submission ports (465/587) have historically been harder to secure — older Postal versions have STARTTLS/certificate problems there. This connector sends over the already-valid HTTPS API endpoint using a scoped, revocable server API key, so it sidesteps the SMTP TLS stack entirely while keeping delivery on your own infrastructure.

Because PHPMailer's fully-assembled MIME message is delivered via /api/v1/send/raw, multipart bodies, inline images, attachments, custom headers and DKIM-relevant structure are transmitted byte-for-byte — exactly what SMTP would have carried.

Requirements

  • WordPress 5.5+
  • PHP 7.4+
  • The FluentSMTP plugin, installed and active
  • A Postal server with an API credential (Server → Credentials → New Credential → type API) and a verified sending domain

Installation

  1. Install and activate FluentSMTP.
  2. Install and activate this plugin.
  3. Go to Settings → Postal (FluentSMTP) and add a connection:
    • Postal Server URL — e.g. https://postal.example.com
    • Server API Key — the API credential from your Postal server
    • From Email / Name — a sender on a domain verified in Postal
  4. Click Test Connection, then Save. Use Send Test to send a real email through Postal.

Saved connections appear in FluentSMTP and are used automatically for matching From addresses, including FluentSMTP's email logging, fallback connections and resend-from-log.

Storing the API key in wp-config.php (optional)

Instead of the database, choose "Store API Keys in Config File" and add:

define( 'FLUENTSMTP_POSTAL_API_KEY', 'your-postal-api-key' );

When stored in the database, the key is encrypted at rest using your WordPress security keys (requires the OpenSSL PHP extension).

Security notes

  • Delivery is over HTTPS to the URL you configure; the API key is sent only in the X-Server-API-Key header.
  • Verify SSL Certificate is on by default. Only disable it for self-signed certificates on isolated lab servers — the connection stays encrypted but is no longer authenticated.
  • The sending domain must be verified on your Postal server, otherwise Postal rejects the message as an unauthenticated From address.

Development

The admin setup screen is a Vue 2 + Element UI app built with Laravel Mix, using the same stack and component conventions as FluentSMTP so the provider form can be merged upstream.

npm install
npm run prod      # build assets/ (committed)
npm run watch     # develop
composer install  # dev-only: PHP lint / phpcs

The compiled bundle in assets/ is committed so the plugin runs on install.

Upstream merge

This connector is structured so FluentSMTP's maintainers can adopt Postal as a first-class provider with mostly file moves. See merge/README.md.

License

GPL-2.0-or-later.