Has anyone been able to get this to work? I've got ChatGPT to output what looked like decent instructions and have fllowed them but keep getting a "Error 400: redirect_uri_mismatch" error. I'll post the instructions below...

To configure OAuth for sending emails via a Google account on a DotNetNuke (DNN) 9 website, you'll need to perform the following steps, both on the DNN side and in the Google Cloud Console. This setup replaces traditional SMTP configurations, enhancing security.

Part 1: Set Up Google OAuth for Email

Step 1: Create a Google Cloud Project

1. Log into Google Cloud Console: Go to Google Cloud Console.
2. Create a New Project:
   • Click the project dropdown on the top navigation bar.
   • Select New Project.
   • Name the project (e.g., "DNN Email OAuth"), and click Create.
3. Enable Gmail API:
   • In your project dashboard, click on APIs & Services → Library.
   • Search for Gmail API and click on it.
   • Click Enable.

Step 2: Create OAuth 2.0 Credentials

1. Create OAuth Credentials:

   • In the API & Services section, navigate to Credentials.
   • Click Create Credentials → OAuth 2.0 Client IDs.
   • Select Web application for the application type.
   • Add a name (e.g., "DNN OAuth Email").
   • Under Authorized redirect URIs, add a dummy URI (e.g., <code><a href="https://your-dnn-site.com/oauth2/callback" target="_blank" rel="nofollow">https://your-dnn-site.com/oauth2/callback</a></code>).
   • Click Create.

2. Get OAuth Credentials:

   • Once created, you'll receive a Client ID and Client Secret. Save these as you will need them for your DNN configuration.

Step 3: Set Up OAuth Consent Screen

1. Configure OAuth Consent Screen:
   • Go to OAuth consent screen under APIs & Services.
   • Set the user type to External.
   • Fill out the required fields such as the application name (e.g., "DNN Email OAuth") and add your website domain.
   • Add your email address and the required information under the Authorized domains section.

Step 4: Authorize Scopes for Gmail API

1. Set Up OAuth Scopes:
   • Under APIs & Services → OAuth Consent Screen, add the Gmail API scope.
   • Add the following scope for Gmail API: <code><a href="https://www.googleapis.com/auth/gmail.send" target="_blank" rel="nofollow">https://www.googleapis.com/auth/gmail.send</a></code>.

Part 2: Configure DotNetNuke to Use OAuth for Google Email

Step 1: Access SMTP Settings in DNN

1. Log into DNN as an administrator or superuser.
2. Navigate to Settings → Servers.
3. Click on SMTP Server Settings.

Step 2: Input OAuth Settings

1. Configure SMTP:
   • SMTP Mode: Select OAuth2.
   • SMTP Server: Use <code>smtp.gmail.com</code>.
   • SMTP Port: Use port <code>587</code> for TLS or <code>465</code> for SSL.
   • SMTP Authentication: Set it to OAuth2.
2. Client ID & Secret:
   • Enter the Client ID and Client Secret obtained from Google Cloud.
3. Authorization Endpoint:
   • Use the authorization URL: <code><a href="https://accounts.google.com/o/oauth2/auth" target="_blank" rel="nofollow">https://accounts.google.com/o/oauth2/auth</a></code>.
4. Token Endpoint:
   • Use the token URL: <code><a href="https://oauth2.googleapis.com/token" target="_blank" rel="nofollow">https://oauth2.googleapis.com/token</a></code>.
5. Redirect URI:
   • Set this to the URI used in your Google Cloud setup (e.g., <code><a href="https://your-dnn-site.com/oauth2/callback" target="_blank" rel="nofollow">https://your-dnn-site.com/oauth2/callback</a></code>).

Step 3: Test the Configuration

1. Save your settings and click Test SMTP Settings to ensure that everything is correctly configured.
2. If successful, DNN will now use Gmail via OAuth for sending emails.