---
title: "Microsoft 365 / Outlook"
description: "Connect Microsoft 365 or Outlook.com to BooleanSMTP through the Microsoft Graph API with your own Azure app, choose where credentials live, and confirm a test email delivered."
image: "https://booleansmtp.com/docs/og.png"
---

> Documentation Index
> Fetch the complete documentation index at: https://booleansmtp.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Microsoft 365 / Outlook

import { Steps, Aside } from '@booleanpress/nimbus/components';

BooleanSMTP connects to Microsoft 365 or Outlook.com through the **Microsoft Graph API**, the only
delivery mode on the free plan. Microsoft has disabled SMTP AUTH Basic Authentication by default for
new tenants and is phasing it out for existing ones, and there's no app-password equivalent for a
Microsoft 365 mailbox the way Google offers one for Gmail; Graph sends the same mail without that
expiry risk. Registering a small Azure app is the only setup cost, and it takes a few minutes.

## Before you begin

- Access to the [Microsoft Entra admin center](https://entra.microsoft.com/) to register an app; any
  work or school account allowed to register apps, or your own personal Microsoft account, can do
  this.
- The mailbox address you'll send from. A personal `outlook.com`, `hotmail.com`, `live.com` or
  `msn.com` mailbox and a paid Microsoft 365 work or school mailbox both work the same way.

## Add the connection

1. In your WordPress admin sidebar, go to **BooleanSMTP → Mailers**.
2. Click **Add Connection** and choose **Microsoft Outlook**.
3. Under **Sender Settings**, fill in **From Email** (the mailbox you'll authorize) and **From Name**.

## Microsoft Graph (OAuth)

1. In the [Microsoft Entra admin center](https://entra.microsoft.com/), go to **App registrations →
   New registration** and register a **Web** app, choosing the account type based on who should be
   able to sign in; see [Tenant ID](#tenant-id) below before picking this.
2. Under **Redirect URI**, paste the exact value BooleanSMTP shows as **Authorized Redirect URI** on
   the connection form you opened above, then save.
3. Go to **Certificates & secrets → New client secret**, and copy the **Value** immediately, not the
   Secret ID; Microsoft shows it once.
4. Go to **API permissions → Add a permission → Microsoft Graph → Delegated permissions**, and add
   `Mail.Send`, `User.Read`, and `offline_access`. Add `Mail.Send.Shared` too if you plan to use
   [Sending as a shared mailbox](#sending-as-a-shared-mailbox).
5. Back on the connection form, paste the **Client ID** and **Client Secret**, and set **Tenant ID**.
6. Click **Authorize** and complete Microsoft's consent screen.
7. Click **Save Mailer** to finish.

![The Microsoft Outlook connection form, with Client ID, Client Secret, Tenant ID, Authorized Redirect URI and Send as a shared mailbox fields, and the Authorize button.](../../../assets/screenshots/outlook.webp "Microsoft Outlook connection form")

The **Authorized Redirect URI** shown isn't your own site's address; it's a fixed one at
`oauth.booleansmtp.com`, the same relay [Google Workspace](/docs/mailers/google/) uses for its own Gmail
API connections. Google requires an OAuth client's redirect URI to be an exact, stable HTTPS address,
and a site's own URL can change; this fixed relay immediately forwards your browser back to your own
site to finish the connection, and only ever sees the one-time authorization code Microsoft issues in
the URL. Your Client Secret stays on your own site, and the resulting access and refresh tokens come
back to your site directly from Microsoft, never through the relay.

> **Tip**
>
> Before clicking **Authorize**, click **Check app credentials** to confirm Microsoft accepts your
> Client ID, Client Secret and Tenant ID right away, without completing the full consent screen: a
> wrong value fails immediately instead of after you've signed in.

### Tenant ID

Leave **Tenant ID** as **common** unless you need to restrict sign-in to one organization; then use
your tenant's GUID (Entra admin center → your app → **Overview** → **Directory (tenant) ID**). Once
you've entered a Client ID and a real tenant (not `common`, `organizations` or `consumers`),
BooleanSMTP shows a **Grant admin consent for your organization** button next to the credential
fields, letting an administrator approve the app for everyone in the organization in one step instead
of every mailbox owner consenting individually; it opens in a new tab. This button only appears with
**Database** credential storage; see [Choose where credentials are stored](#choose-where-credentials-are-stored)
below.

### Sending as a shared mailbox

Enable **Send as a shared mailbox**, set **From Email** to the shared mailbox's address, and
authorize with an account that has Exchange **"Send As"** or **"Send on behalf"** rights to that
mailbox, not the shared mailbox's own login (shared mailboxes typically don't have one). Make sure the
Entra app also has the `Mail.Send.Shared` delegated permission from step 4 above.

## Choose where credentials are stored

Like every BooleanSMTP mailer, **Credential Storage** offers **Database**, **WP Config**, or
**Environment** for the **Client ID**, **Client Secret**, and **Tenant ID** fields. In **WP Config**
or **Environment** mode, leave those fields blank in the form and instead define:

```php
define('BOOLEANSMTP_OUTLOOK_CLIENT_ID', '...');
define('BOOLEANSMTP_OUTLOOK_CLIENT_SECRET', '...');
define('BOOLEANSMTP_OUTLOOK_TENANT_ID', 'common'); // or your tenant's GUID
```

As **Environment**, define the same names as OS environment variables instead of PHP constants. See
[Storing credentials in wp-config](/docs/advanced/wp-config-credentials/) for the general naming rule.

Whichever you choose, you still click **Authorize** once to grant BooleanSMTP an OAuth token for the
mailbox: moving the app credentials out of the database doesn't skip Microsoft's consent screen, and
the access and refresh tokens it returns are stored encrypted in the database regardless, the same as
any other OAuth connection.

## Send a test email

Use **Test Email** in the sidebar to confirm the connection works: see
[Send a test email](/docs/getting-started/send-a-test-email/) for the steps.

A successful-looking result inside BooleanSMTP is the first signal, not the only one worth checking:

- **In your inbox**: confirm the email actually arrived, checking spam or junk first.
- **In [Email Logs](/docs/logs/)**: find the send and confirm its status.
- **On the connection itself**: reopen it (the pencil icon under **Actions**) and confirm it still
  shows **Account connected** with the authorized mailbox's address, rather than prompting you to
  reconnect.

## Common errors

- **"redirect_uri_mismatch"**: the URI pasted into the Entra app registration doesn't exactly match
  the one BooleanSMTP shows as **Authorized Redirect URI**, including the scheme and any trailing
  slash.
- **"Check app credentials" fails right away**: Microsoft rejected the Client ID, Client Secret, or
  Tenant ID itself, before any sign-in happens; re-check all three against the Entra app registration.
- **401 with an empty body on `/me/sendMail`, but `/me` still returns 200**: the signed-in identity
  has no mailbox in this tenant, often a guest (`#EXT#`) account; reconnect with a mailbox-enabled
  account, or set **Tenant ID** to `common` if this is meant to be a personal or multi-tenant setup.
- **"...does not have the right to send mail on behalf of the specified sending account"**: the
  authorizing account lacks Exchange delegate rights to the mailbox in **From Email**; see
  [Sending as a shared mailbox](#sending-as-a-shared-mailbox) above.
- **A previously working SMTP connection stopped working**: Outlook has no SMTP mode; switch to the
  Microsoft Graph setup on this page.

## Next steps

- [Send a test email](/docs/getting-started/send-a-test-email/)
- [Set a fallback connection](/docs/advanced/fallback-and-retries/)
- [Storing credentials in wp-config](/docs/advanced/wp-config-credentials/)
- [Check delivery in Logs](/docs/logs/)
- [Set up alerts](/docs/alerts/)

Source: https://booleansmtp.com/docs/mailers/outlook/index.mdx