DEV Community

Cover image for Real-Time Email Notifications in .NET Using Microsoft Graph API
Madusanka Bandara
Madusanka Bandara

Posted on

Real-Time Email Notifications in .NET Using Microsoft Graph API

#api #dotnet #azure #microsoftgraph

Monitoring emails in real-time is a common requirement for businesses. With Microsoft Graph API, you can automatically log email details, download attachments, and maintain daily logs. In this article, we’ll create a .NET Web API to handle email notifications.

1. Introduction

Microsoft Graph API provides access to Office 365 services like emails, calendars, and users.

With this setup, we can:

  • Subscribe to a user’s inbox
  • Receive webhook notifications for new emails
  • Log email details to a file in JSON format
  • Download attachments automatically

This is useful for automated email monitoring and reporting.

2. Prerequisites

Before starting, ensure you have:

  • .NET 6/7/8 project
  • Visual Studio or VS Code
  • Office 365 account

  • NuGet packages:

    Microsoft.Graph  
Azure.Identity
Newtonsoft.Json

3. Setting Up Microsoft Graph API

3.1 Register an Application in Azure

i. Go to Azure Portal (https://portal.azure.com/) → App Registrations → New Registration

ii. Provide a name (GraphNotificationDemo), Supported account types (Accounts in any organizational directory and personal Microsoft accounts) and redirect URI (https://localhost)

Click Register.

iii. Note down the Application (client) ID and Directory (tenant) ID for later use.

iv. Add a client secret (Manage → Certificates & secrets → New client secret → Enter a "Description", and select the "Expires" duration.

Click Add.

v. Note down the client secret value for future reference.

vi. API Permissions (Manage → API Permissions → Add a permission → Microsoft Graph)

vii. Add API permissions:

Mail.Read
Mail.ReadWrite
Mail.ReadBasic
Enter fullscreen mode Exit fullscreen mode

4. Ngrok

Ngrok allows calls from the internet to be directed to your application running locally without needing to create firewall rules.

Install Ngrok from https://ngrok.com/

On the command prompt, Run below command:

ngrok http 5000
Enter fullscreen mode Exit fullscreen mode

5. Create an ASP.NET Core web API project

i. Open Visual Studio 2022 and create a new project. From the available templates, select ASP.NET Core Web API.

ii. Give your project a specific name and choose the location where you want to save it. After that, click the Next button.

iii. In the next step, select the framework as .NET 8 (LTS), since it is the latest long-term support version. Finally, click Create to generate your new Web API project.

iv. Add the below NuGet packages to the project.

Azure.Identity
Microsoft.Graph
Newtonsoft.Json
Enter fullscreen mode Exit fullscreen mode

v. Create a configuration class:

public class MyConfig
{
    public string AppId { get; set; }
    public string TenantId { get; set; }
    public string AppSecret { get; set; }
    public string Ngrok { get; set; }
}
Enter fullscreen mode Exit fullscreen mode

vi. Add your credentials in appsettings.json.

"MyConfig": {
  "AppId": <<--YOUR CLIENT ID-->>,
  "AppSecret": <<--YOUR CLIENT Secret-->>,
  "TenantId": <<--YOUR Tenant Id-->>,
  "Ngrok": <<--YOUR Ngrok URL-->>
}
Enter fullscreen mode Exit fullscreen mode

vii. Update Program.cs file:

using changenotifications.Models;

var config = new MyConfig();
builder.Configuration.Bind("MyConfig", config);
builder.Services.AddSingleton(config);

//app.UseHttpsRedirection(); -- comment out the following line to disable SSL redirection.
Enter fullscreen mode Exit fullscreen mode

viii. Subscribing to a User Inbox:

What is a subscription?

A subscription tells Graph API to send POST requests to your server whenever a new email arrives. Subscriptions expire, so we’ll set up auto-renew.

var subscription = new Subscription
{
    ChangeType = "created",
    NotificationUrl = $"{config.Ngrok}/api/notifications",
    Resource = $"/users/{userId}/mailFolders('Inbox')/messages",
    ExpirationDateTime = DateTime.UtcNow.AddMinutes(5),
    ClientState = "SecretClientState"
};

var newSubscription = await graphClient.Subscriptions.PostAsync(subscription);
Enter fullscreen mode Exit fullscreen mode

ix. Webhook Endpoint

Create a [HttpPost] endpoint to receive notifications:

[HttpPost]
public async Task<ActionResult> Post([FromQuery] string validationToken)
{
    if (!string.IsNullOrEmpty(validationToken))
    return Ok(validationToken); // Graph validation
}
Enter fullscreen mode Exit fullscreen mode

x. Parsing Notifications

After receiving a POST, extract userId and messageId to fetch the full email:

var message = await graphClient.Users[userId].Messages[messageId].GetAsync();
Enter fullscreen mode Exit fullscreen mode

xi. Logging Email Details

We log key email details such as the subject, sender, recipients (To & CC), received and sent dates, body preview, and attachments.

var logFile = Path.Combine(BaseDir, "logs", $"EmailLog_{DateTime.UtcNow:yyyyMMdd}.txt");
await File.AppendAllTextAsync(logFile, JsonSerializer.Serialize(logEntry, new JsonSerializerOptions { WriteIndented = true }));
Enter fullscreen mode Exit fullscreen mode

xii. Downloading Attachments

If the email has attachments, save them in a folder:

if (attachment is FileAttachment fileAtt)
{
    var savePath = Path.Combine(msgFolder, fileAtt.Name);
    await File.WriteAllBytesAsync(savePath, fileAtt.ContentBytes);
}
Enter fullscreen mode Exit fullscreen mode

Folder structure:

C:\EmailAttachments\20250819\<MessageId>\
Enter fullscreen mode Exit fullscreen mode

xiii. Auto-Renew Subscriptions

Subscriptions expire. Use a Timer to renew:

if (subscription.ExpirationDateTime < DateTime.UtcNow.AddMinutes(2))
RenewSubscription(subscription);
Enter fullscreen mode Exit fullscreen mode

6. Test the application

i. Open Swagger in the browser, trigger the subscribe-inbox GET endpoint from the Notifications controller, and you will receive a response like below.

After subscribing, the system sends an email to the user, logs all email details, and saves any email attachments in the file path C:\EmailAttachments.

7. Summary

In this article, we learned how to use Microsoft Graph API with .NET to read emails, create inbox subscriptions, handle real-time notifications, log email details into daily text files, and download attachments. We also covered how to set up auto-renewal for subscriptions to keep the system running continuously. With this setup, you can build a reliable email monitoring and processing system for business or personal applications.

8. Code Download

The code developed during this article can be found here.

Top comments (0)