DixonSMTP for Outlook & Microsoft 365

WordPress’ default PHP mail() delivery is frequently blocked or spam-foldered. DixonSMTP for Outlook & Microsoft 365 routes every email your site sends (core, WooCommerce, WPForms, Contact Form 7, Gravity Forms, and anything else using wp_mail()) through Microsoft’s SMTP servers — authenticated, encrypted, and deliverable.

100% free. No premium upsell, no paid tiers, no feature gating.

Why OAuth 2.0?

Microsoft has deprecated Basic Authentication for Exchange Online and is progressively disabling password-based SMTP AUTH (new Microsoft 365 tenants have it off by default). OAuth 2.0 (“Modern Authentication”) is the supported, secure path forward — which is why this plugin is OAuth-only by design. It implements the full Microsoft identity platform authorization code flow with automatic token refresh, so you sign in once and it keeps working.

Features

• OAuth 2.0 (Modern Auth) for Microsoft 365 / Entra ID — authorization code flow, automatic access-token refresh, encrypted token storage
• From Email / From Name with optional force-override (recommended — Microsoft rejects mismatched senders)
• Test email tool with a full SMTP debug transcript
• Email log (last 10–500 emails, configurable) with status and error details in a custom table
• Optional fallback to the default PHP mailer when SMTP fails
• Failure notifications to the site admin after repeated errors (rate-limited)
• Debug mode compatible with WP_DEBUG_LOG
• Multisite compatible (network activation supported; settings are per-site)
• Secrets (client secret, OAuth tokens) stored encrypted (AES-256 keyed from your WordPress salts)
• Translation-ready, fully sanitized/escaped, capability + nonce protected

Compatibility

Works with any plugin that sends mail through wp_mail(): WPForms, Contact Form 7, Gravity Forms, Ninja Forms, WooCommerce, Easy Digital Downloads, membership and newsletter plugins, etc.

Microsoft 365 / Azure OAuth Setup

You need a (free) app registration in Microsoft Entra ID. One-time setup, about 5 minutes:

1. Register the application

1. Sign in to https://entra.microsoft.com (or the Azure Portal → Microsoft Entra ID).
2. Go to Identity → Applications → App registrations → New registration.
3. Name: e.g. WordPress SMTP.
4. Supported account types:
   • Accounts in this organizational directory only — single company tenant (most common; use your Tenant ID in the plugin).
   • Accounts in any organizational directory and personal Microsoft accounts — needed for personal Outlook.com mailboxes (use common in the plugin).
5. Redirect URI: choose platform Web and paste the exact Redirect URI shown on the plugin’s OAuth 2.0 tab
   (it looks like https://your-site.com/wp-json/dxn-outlook/v1/callback).
6. Click Register.

2. Collect the IDs

• On the app’s Overview page copy the Application (client) ID and Directory (tenant) ID into the plugin’s OAuth tab.

3. Create a client secret

1. Go to Certificates & secrets → New client secret.
2. Choose an expiry (set a calendar reminder — you must rotate it before expiry!).
3. Copy the secret Value (not the Secret ID) immediately — it is shown only once — and paste it into the plugin.

4. Add API permissions

1. Go to API permissions → Add a permission.
2. Choose APIs my organization uses and search for Office 365 Exchange Online
   (or use Microsoft Graph → Delegated if SMTP.Send appears there in your tenant).
3. Select Delegated permissions → SMTP.Send, then Add.
4. offline_access, openid, profile, email are requested automatically at sign-in; no admin action usually needed. If your tenant requires it, click Grant admin consent.

5. Enable SMTP AUTH for the mailbox

Even with OAuth, Exchange Online requires SMTP AUTH to be allowed for the sending mailbox:

• Microsoft 365 admin center → Users → Active users → select user → Mail → Manage email apps → check Authenticated SMTP, or
• PowerShell: Set-CASMailbox -Identity user@domain.com -SmtpClientAuthenticationDisabled $false

6. Authorize the plugin

1. Save the Client ID, Client Secret and Tenant ID on the plugin’s OAuth 2.0 tab.
2. Click Sign in with Microsoft & Authorize and sign in with the mailbox that should send email.
3. When you return, the status shows Connected. Send a test email.

External Services

This plugin connects to Microsoft services in order to authenticate and deliver email. No data is sent to the plugin author or any other third party.

• Microsoft identity platform (login.microsoftonline.com) — used for OAuth 2.0 sign-in and token refresh. Sends your Azure app Client ID, Client Secret, authorization codes and refresh tokens. Contacted when you click “Sign in with Microsoft” and automatically before sending when the access token needs refreshing.
• Microsoft SMTP servers (smtp.office365.com or the host you configure) — used to deliver email. Sends the email content, sender and recipient addresses, and an OAuth access token for authentication. Contacted on every outgoing email.

These services are provided by Microsoft: Terms of Use, Privacy Statement.