Relaymint

Reliable email delivery for WordPress via SMTP or Microsoft 365 / Outlook — with email log, smart routing, background sending and rate limiting.

Documentation (German): detailed setup guides, reference and troubleshooting in the Relaymint Wiki.

Description

Relaymint replaces the default PHP mail() transport of WordPress with an authenticated SMTP connection or the Microsoft Graph API (Microsoft 365 / Outlook), so emails from WordPress core, plugins and themes actually reach the inbox. Every email is logged, can be routed through different SMTP accounts based on rules, and can optionally be sent in the background with rate limits — a self-hosted alternative to plugins like Easy WP SMTP.

Features

• SMTP mailer — host, port, encryption (none / SSL / TLS), Auto TLS, authentication, From email/name (optionally forced), return path.
• Microsoft 365 / Outlook mailer — sends through the Microsoft Graph API with OAuth 2.0 instead of SMTP AUTH: sign in with the mailbox once (Microsoft 365 and Outlook.com) or use app-only access with the application permission Mail.Send (Microsoft 365). Tokens are renewed automatically.
• Encrypted credentials — SMTP passwords, Microsoft client secrets and OAuth tokens are stored with AES-256-GCM (key derived from the WordPress salts) or defined as constants in wp-config.php.
• Email log — status (sent, failed, queued, blocked), recipients, connection, initiating plugin/theme, error messages; optional storage of content and headers; search, status filter, detail view with sandboxed HTML preview, resend, bulk delete and automatic retention.
• Smart Routing — additional connections (SMTP or Microsoft 365 / Outlook) plus rules (subject, message, from, to, cc, bcc, reply-to, header, initiator × contains / is / starts with / ends with / regex and their negations). Conditions within a group are AND-combined, groups are OR-combined, first matching route wins.
• Domain check — only use SMTP on allowed site domains (e.g. to keep staging copies off the production mail account), optionally block all emails on a mismatch.
• Do Not Send — block all outgoing emails (they are still logged).
• Allow insecure SSL certificates — for SMTP servers with self-signed certificates.
• Debug log — SMTP transcripts with masked credentials; errors are always recorded.
• Optimize email sending — emails are queued and sent in the background via the bundled Action Scheduler. Attachments are copied to a protected directory until the email is sent.
• Email rate limiting — max. emails per minute / hour / day / week; emails above the limit wait in the queue.
• Test email — send a test via any connection and see the full SMTP debug output.
• Unified admin design — all Relaymint screens use the bundled WP-Backend UI design system shared by our plugins (page header, cards, badges, tabs).
• German translation included.

Requirements

• WordPress 6.9 or higher (required by the bundled Action Scheduler 4.2)
• PHP 7.4 or higher with the OpenSSL extension
• An SMTP account (any provider) or a Microsoft 365 / Outlook.com mailbox with an app registration in Microsoft Entra ID
• Bundled, nothing to install: Action Scheduler 4.2.0, Plugin Update Checker 5.7 and WP-Backend UI 1.0.2 (shared admin design system)

Installation

From GitHub

1. Download relaymint.zip from the latest release on the Releases page.
2. Upload it via Plugins → Add New → Upload Plugin.
3. Activate the plugin.

Manual

cd wp-content/plugins
git clone https://github.com/mrclksr2409/Relaymint.git relaymint

Usage

1. Go to Relaymint → Settings → General, choose the mailer (SMTP or Microsoft 365 / Outlook) and enter the data of your provider.
2. Send a test email under Relaymint → Tools.
3. Optional: add more SMTP accounts under Additional Connections and create rules under Smart Routing.
4. Configure logging under Email Log and the remaining options under Misc.
5. Sent emails are listed under Relaymint → Email Log.

Microsoft 365 / Outlook

Relaymint sends via the Microsoft Graph sendMail API. The message is built by PHPMailer as usual and handed to Graph as MIME, so HTML, attachments, Cc, Bcc and Reply-To work as with SMTP. SMTP AUTH does not have to be enabled for the mailbox.

1. In the Microsoft Entra admin center open App registrations → New registration.
   • Supported account types: your organization only, or any organization and personal Microsoft accounts for Outlook.com.
   • Redirect URI: platform Web, value as shown in the Relaymint connection settings (https://your-site/wp-admin/admin-post.php). HTTPS is required.
2. Certificates & secrets → New client secret, copy the secret value.
3. API permissions → Microsoft Graph:
   • Sign in with the mailbox (delegated): Mail.Send, User.Read, offline_access.
   • App-only (application): Mail.Send, then Grant admin consent. Restrict the app to the sending mailbox with an application access policy / RBAC for applications.
4. In Relaymint select Microsoft 365 / Outlook, enter tenant ID, client ID and secret and save.
   • Delegated: click Connect with Microsoft and sign in with the sending mailbox. Leave From Email empty to send as that mailbox; other addresses need Send As rights.
   • App-only: set the tenant ID (not common) and the From Email of a mailbox in your tenant.
5. Send a test email under Relaymint → Tools.

Notes: Graph accepts messages up to about 4 MB per request (including base64 encoded attachments). Client secrets expire — renew them in Entra and enter the new value in time. Changing tenant, client ID or authentication mode requires signing in again.

Constants for wp-config.php

Defined constants override the stored settings and lock the corresponding field in the admin.

// Primary connection.
define( 'RELAYMINT_SMTP_HOST', 'smtp.example.com' );
define( 'RELAYMINT_SMTP_PORT', 587 );
define( 'RELAYMINT_SMTP_ENCRYPTION', 'tls' ); // none | ssl | tls
define( 'RELAYMINT_SMTP_USER', 'user@example.com' );
define( 'RELAYMINT_SMTP_PASS', 'secret' );
define( 'RELAYMINT_FROM_EMAIL', 'noreply@example.com' );
define( 'RELAYMINT_FROM_NAME', 'Example' );

// Primary connection via Microsoft 365 / Outlook.
define( 'RELAYMINT_MAILER', 'microsoft' ); // smtp | microsoft
define( 'RELAYMINT_MS_TENANT', 'contoso.onmicrosoft.com' );
define( 'RELAYMINT_MS_CLIENT_ID', '00000000-0000-0000-0000-000000000000' );
define( 'RELAYMINT_MS_CLIENT_SECRET', 'secret' );

// Password of an additional connection (the ID is shown in the connection list).
define( 'RELAYMINT_SMTP_PASS_CABC12345', 'secret' );
// Client secret of an additional Microsoft connection.
define( 'RELAYMINT_MS_CLIENT_SECRET_CABC12345', 'secret' );

Note: Stored passwords, client secrets and OAuth tokens are encrypted with a key derived from AUTH_KEY, SECURE_AUTH_KEY and LOGGED_IN_KEY. If you change these salts, re-enter the SMTP passwords / client secrets and reconnect Microsoft accounts.

How the options interact

1. Do Not Send blocks everything (logged as blocked).
2. Domain check mismatch → block all (if enabled) or send without SMTP via PHP mail().
3. Optimize Email Sending → the email is queued and wp_mail() returns true immediately.
4. Smart Routing picks the connection (falls back to the primary connection).
5. Rate limiting is applied when the queue is processed, so it requires Optimize Email Sending.

Updates

This plugin uses the Plugin Update Checker library to deliver updates directly from GitHub Releases. Once installed, WordPress will check for updates automatically (every 12 hours by default) and show them on the standard Dashboard → Updates screen. You can trigger a manual check via Plugins → Check for updates.

Under Settings → Misc → Update Channel you can choose the source:

• Stable (default) — GitHub Releases of the main branch.
• Beta — the current head of the beta branch. An update is offered as soon as the Version header in relaymint.php on beta is higher than the installed version. Not intended for production sites.

Switching the channel clears the cached update data. Switching back from beta to stable does not downgrade; the next stable release is installed once its version is higher than the installed beta.

Releases are built by .github/workflows/release.yml: pushing a tag vX.Y.Z creates relaymint.zip and attaches it to the GitHub release of that tag.

Hooks & Filters

Actions

Filters

$mail is a Relaymint_Mail_Data object ($mail->atts holds the original wp_mail() arguments).

Development

git clone https://github.com/mrclksr2409/Relaymint.git
cd Relaymint
# Coding standards (WPCS 3):
phpcs            # uses phpcs.xml.dist
# Regenerate translations:
wp i18n make-pot . languages/relaymint.pot --exclude=libraries,plugin-update-checker
wp i18n make-mo languages/

Bundled libraries (do not edit): libraries/action-scheduler/ (Action Scheduler 4.2.0), libraries/wp-backend-ui/ (WP-Backend UI 1.0.2, shared admin design system) and plugin-update-checker/ (PUC 5.7).

To update WP-Backend UI, replace libraries/wp-backend-ui/ with the new release (only wp-backend-ui.php, includes/, assets/ and README.md). If several plugins bundle the library, the newest copy is loaded.

Changelog

[0.4.3] — 2026-11-04

Fixed

• Microsoft Graph: on HTTP 403 the send is retried once with a freshly requested access token. Previously a token cached before admin consent was granted kept failing with ErrorAccessDenied until it expired.

Added

• The transcript shows tenant, app ID and permissions (roles/scp) of the access token used (never the token itself), plus hints on the likely cause of a 403.

[0.4.2] — 2026-10-12

Geändert

• Plugin Update Checker auf v5.7 aktualisiert.

[0.4.1] — 2026-10-10

Changed

• Author URI now points to the GitHub profile.
• New "Wiki" link in the plugin row on the Plugins screen.

[0.4.0] — 2026-10-10

Added

• Microsoft 365 / Outlook mailer via the Microsoft Graph API (OAuth 2.0): sign in with the mailbox (delegated, authorization code flow with PKCE, Microsoft 365 and Outlook.com) or app-only access (client credentials, Microsoft 365). Available for the primary and additional connections, Smart Routing and the test email.
• Encrypted storage of client secrets and OAuth tokens, automatic token renewal, RELAYMINT_MAILER / RELAYMINT_MS_* constants.

Changed

• Connection settings start with a mailer selection; the connection list shows how each connection sends.

[0.3.0] — 2026-10-09

Added

• Update channel setting (Misc tab): stable (GitHub Releases from main) or beta (beta branch).

[0.2.0] — 2026-10-09

Changed

• Unified admin design via the bundled WP-Backend UI 1.0.2 (libraries/wp-backend-ui/): shared page header with version badge, tabs, cards and design tokens on Settings, Email Log and Tools.
• Email log: status pills are now badges; the detail view shows the entry as a card with a key/value list, headers and message in cards, Back/Resend in the header.
• Tools: test email and debug log are shown as cards; test results as inline alerts.
• Smart Routing routes and the domain check / rate limit sub-options are shown as cards.
• Confirmation dialogs use the library's data-wpb-confirm; assets/css/admin.css only contains Relaymint-specific layout.

[0.1.0] — 2026-10-09

Added

• SMTP mailer with encrypted credentials and wp-config.php overrides.
• Email log with search, filters, detail view, resend and retention.
• Smart Routing with additional connections.
• Domain check, Do Not Send, insecure SSL option, debug log.
• Background sending via Action Scheduler and email rate limiting.
• Test email tool, German translation.

License

GPL-2.0-or-later. See LICENSE.