C#/ASP.NET/ASP MVC - Send Email using Microsoft OAuth 2.0 (Modern Authentication) + EWS Protocol from Office 365 Account

You can send email using traditional user/password authentication from Office 365 account by EWS Protocol.

However Microsoft will disable traditional user authentication in the future, switching to Microsoft OAuth (Modern Authentication) is strongly recommended now.

Installation

Before you can use the following codes, please download EASendMail SMTP Component and install it on your machine at first. Full sample proejcts are included in this installer.

Install from NuGet

You can also install the run-time assembly by NuGet. Run the following command in the NuGet Package Manager Console:

Install-Package EASendMail

Note

If you install it by NuGet, no sample projects are installed, only .NET assembly is installed.

Add Reference

To use EASendMail SMTP Component in your project, the first step is Add reference of EASendMail to your project. Please create or open your project with Visual Studio, then go to menu -> Project -> Add Reference -> .NET -> Browse..., and select Installation Path\Lib\net[version]\EASendMail.dll from your disk, click Open -> OK, the reference of EASendMail will be added to your project, and you can start to use it to send email in your project.

add reference in c#/vb.net/c++/cli/clr

.NET Assembly

Because EASendMail has separate builds for .Net Framework, please refer to the following table and choose the correct dll.

Separate builds of run-time assembly for .NET Framework 1.1, 2.0, 3.5, 4.0, 4.5, 4.6.1, .NET Core 2.1 and .NET Compact Framework 2.0, 3.5.

File .NET Framework Version
Lib\net11\EASendMail.dll Built with .NET Framework 1.1
It requires .NET Framework 1.1, 2.0, 3.5 or later version.
Lib\net20\EASendMail.dll Built with .NET Framework 2.0
It requires .NET Framework 2.0, 3.5 or later version.
Lib\net35\EASendMail.dll Built with .NET Framework 3.5
It requires .NET Framework 3.5 or later version.
Lib\net40\EASendMail.dll Built with .NET Framework 4.0
It requires .NET Framework 4.0 or later version.
Lib\net45\EASendMail.dll Built with .NET Framework 4.5
It requires .NET Framework 4.5 or later version.
Lib\net461\EASendMail.dll Built with .NET Framework 4.6.1
It requires .NET Framework 4.6.1 or later version.
Lib\netcoreapp2.1\EASendMail.dll Built with .NET Core 2.1
It requires .NET Core 2.1 or later version.
Lib\net20-cf\EASendMail.dll Built with .NET Compact Framework 2.0
It requires .NET Compact Framework 2.0, 3.5 or later version.
Lib\net35-cf\EASendMail.dll Built with .NET Compact Framework 3.5
It requires .NET Compact Framework 3.5 or later version.

Create your application in Azure Portal

To use Microsoft/Office365/Live OAuth (Modern Authentication) in your application, you must create a application in https://portal.azure.com.

  • Sign in to the Azure portal using either a work or school account or a personal Microsoft account.

  • If your account gives you access to more than one tenant, select your account in the top right corner, and set your portal session to the Azure AD tenant that you want.

  • In the left-hand navigation pane, select the Azure Active Directory service, and then select App registrations -> New registration.

    azure portal new app registration
  • When the Register an application page appears, enter your application’s registration information:

    azure portal application registration
    • Name - Enter a meaningful application name that will be displayed to users of the app.
    • Supported account types - Select which accounts you would like your application to support. Because we need to support all Office 365 and LIVE SDK (hotmail, outlook personal account) select Accounts "in any organizational directory and personal Microsoft accounts".
  • Redirect URI (optional)

    Select the type of app you’re building, Web or Public client (mobile & desktop), and then enter the redirect URI (or reply URL) for your application.

    For web applications, provide the base URL of your app. For example, http://localhost:31544 might be the URL for a web app running on your local machine. Users would use this URL to sign in to a web client application.

    For public client applications, provide the URI used by Azure AD to return token responses. Enter a value specific to your application, such as myapp://auth.

  • Client Id/secrets

    After you registered your application, Azure AD assigns a unique application (client) ID to your app, and you’re taken to your application’s Overview page. click "Certificates and secrets" -> "client secrets" and add a new client secret.

Important

Please store "client secret" by yourself, because it is hidden when you view it at next time.

API Permission

Click "API Permission" -> "Add a permission" -> "Exchange" -> "Delegated Permission" -> "Check EWS.AccessAsUser.All" -> "Add a permission" -> "Microsoft Graph" -> "Delegated Permission" -> "User.Read", "email", "offline_access", "openid" and "profile".

azure application api permission

Authentication

  • Click "Authentication"

    • Implicit grant: check "Access tokens" and "ID tokens";
    • Redirect URI: input the url to get authorization code, for native desktop application, you don’t have to add redirect uri.
  • Mobile and desktop applications -> Redirect Uri, please check or add the following URI.

    https://login.microsoftonline.com/common/oauth2/nativeclient
    https://login.live.com/oauth20_desktop.srf
    http://127.0.0.1
    

    Note

    • https://login.live.com/oauth20_desktop.srf is used for Live SDK, http://127.0.0.1 is used for local Http Listener.
  • Supported account types:

    Select Accounts in any organizational directory (Any Azure AD directory - Multitenant) and personal Microsoft accounts (e.g. Skype, Xbox)

  • Advanced settings:

    Set both "Live SDK Support" and "Treat application as a public client" to "Yes".

azure application Authentication Overview

Above client id and client secret support both "Office365 + EWS" and "Live (hotmail, outlook personal account) + SMTP", Office365 OAuth doesn’t support SMTP, only EWS is supported.

Use client id and client secret to request access token

You can use client id and client secret to get the user email address and access token like this:

  • Your application uses a web browser/browser control to open Microsoft OAUTH URL;
  • User inputs user and password in Microsoft Web Authentication Page, and then Microsoft returns access token back to your application;
  • Your application uses access token to access Office 365 EWS server.
  • You can find full example codes in EASendMail Installation Path\Samples_{Programming language/Developer Tool}\Oauth project.

Important

You should create your client id and client secret, do not use the client id from example codes in production environment, it is used for test purpose. If you got "This app isn't verified" information, please click "Advanced" -> Go to ... for test.

C# - Send Email Using Microsoft OAuth + Office 365 EWS Protocol

Here is a console application which demonstrates how to use Microsoft OAuth to do user authentication and send email.

Note

This sample cannot handle the event of Web Browser is closed by user manually before authentication is completed. You can refer to the better sample project which uses Web Browser Control in EASendMail installation path.

using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
using EASendMail;

namespace EASendMailKbCSharp
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("+------------------------------------------------------------------+");
            Console.WriteLine("  Sign in with MS OAuth                                             ");
            Console.WriteLine("   If you got \"This app isn't verified\" information in Web Browser, ");
            Console.WriteLine("   click \"Advanced\" -> Go to ... to continue test.");
            Console.WriteLine("+------------------------------------------------------------------+");
            Console.WriteLine("");
            Console.WriteLine("Press any key to sign in...");
            Console.ReadKey();

            try
            {
                Program p = new Program();
                p.DoOauthAndSendEmail();
            }
            catch (Exception ep)
            {
                Console.WriteLine(ep.ToString());
            }
            Console.ReadKey();
        }

        void SendMailWithXOAUTH2(string userEmail, string accessToken)
        {
            // Office365 server address
            SmtpServer oServer = new SmtpServer("outlook.office365.com");

            // use EWS protocol
            oServer.Protocol = ServerProtocol.ExchangeEWS;
            // enable SSL connection
            oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

            // use SMTP OAUTH 2.0 authentication
            oServer.AuthType = SmtpAuthType.XOAUTH2;
            // set user authentication
            oServer.User = userEmail;
            // use access token as password
            oServer.Password = accessToken;

            SmtpMail oMail = new SmtpMail("TryIt");
            // Your email address
            oMail.From = userEmail;

            // Please change recipient address to yours for test
            oMail.To = "support@emailarchitect.net";

            oMail.Subject = "test email from Office365 account with OAUTH 2";
            oMail.TextBody = "this is a test email sent from c# project with EWS.";

            Console.WriteLine("start to send email using OAUTH 2.0 ...");

            SmtpClient oSmtp = new SmtpClient();
            oSmtp.SendMail(oServer, oMail);

            Console.WriteLine("The email has been submitted to server successfully!");
        }

        // client configuration
        // You should create your client id and client secret,
        // do not use the following client id in production environment, it is used for test purpose only.
        const string clientID = "eccbabb2-3377-4265-85c1-ea2fb515f075";
        const string clientSecret = "QaR_RR:-5WqTY[nni9pdBr9xVybqrAu4";
        const string scope = "https://outlook.office.com/EWS.AccessAsUser.All%20offline_access%20email%20openid";
        const string authUri = "https://login.microsoftonline.com/common/oauth2/v2.0/authorize";
        const string tokenUri = "https://login.microsoftonline.com/common/oauth2/v2.0/token";

        static int GetRandomUnusedPort()
        {
            var listener = new TcpListener(IPAddress.Loopback, 0);
            listener.Start();
            var port = ((IPEndPoint)listener.LocalEndpoint).Port;
            listener.Stop();
            return port;
        }

        async void DoOauthAndSendEmail()
        {
            // Creates a redirect URI using an available port on the loopback address.
            string redirectUri = string.Format("http://127.0.0.1:{0}/", GetRandomUnusedPort());
            Console.WriteLine("redirect URI: " + redirectUri);

            // Creates an HttpListener to listen for requests on that redirect URI.
            var http = new HttpListener();
            http.Prefixes.Add(redirectUri);
            Console.WriteLine("Listening ...");
            http.Start();

            // Creates the OAuth 2.0 authorization request.
            string authorizationRequest = string.Format("{0}?response_type=code&scope={1}&redirect_uri={2}&client_id={3}&prompt=login",
                authUri,
                scope,
                Uri.EscapeDataString(redirectUri),
                clientID
            );

            // Opens request in the browser.
            System.Diagnostics.Process.Start(authorizationRequest);

            // Waits for the OAuth authorization response.
            var context = await http.GetContextAsync();

            // Brings the Console to Focus.
            BringConsoleToFront();

            // Sends an HTTP response to the browser.
            var response = context.Response;
            string responseString = string.Format("<html><head></head><body>Please return to the app and close current window.</body></html>");
            var buffer = Encoding.UTF8.GetBytes(responseString);
            response.ContentLength64 = buffer.Length;
            var responseOutput = response.OutputStream;
            Task responseTask = responseOutput.WriteAsync(buffer, 0, buffer.Length).ContinueWith((task) =>
            {
                responseOutput.Close();
                http.Stop();
                Console.WriteLine("HTTP server stopped.");
            });

            // Checks for errors.
            if (context.Request.QueryString.Get("error") != null)
            {
                Console.WriteLine(string.Format("OAuth authorization error: {0}.", context.Request.QueryString.Get("error")));
                return;
            }

            if (context.Request.QueryString.Get("code") == null)
            {
                Console.WriteLine("Malformed authorization response. " + context.Request.QueryString);
                return;
            }

            // extracts the code
            var code = context.Request.QueryString.Get("code");
            Console.WriteLine("Authorization code: " + code);

            string responseText = await RequestAccessToken(code, redirectUri);
            Console.WriteLine(responseText);

            OAuthResponseParser parser = new OAuthResponseParser();
            parser.Load(responseText);

            var user = parser.EmailInIdToken;
            var accessToken = parser.AccessToken;

            Console.WriteLine("User: {0}", user);
            Console.WriteLine("AccessToken: {0}", accessToken);

            SendMailWithXOAUTH2(user, accessToken);
        }

        async Task<string> RequestAccessToken(string code, string redirectUri)
        {
            Console.WriteLine("Exchanging code for tokens...");

            // builds the  request
            string tokenRequestBody = string.Format("code={0}&redirect_uri={1}&client_id={2}&grant_type=authorization_code",
                code,
                Uri.EscapeDataString(redirectUri),
                clientID
                );

            // sends the request
            HttpWebRequest tokenRequest = (HttpWebRequest)WebRequest.Create(tokenUri);
            tokenRequest.Method = "POST";
            tokenRequest.ContentType = "application/x-www-form-urlencoded";
            tokenRequest.Accept = "Accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";

            byte[] _byteVersion = Encoding.ASCII.GetBytes(tokenRequestBody);
            tokenRequest.ContentLength = _byteVersion.Length;

            Stream stream = tokenRequest.GetRequestStream();
            await stream.WriteAsync(_byteVersion, 0, _byteVersion.Length);
            stream.Close();

            try
            {
                // gets the response
                WebResponse tokenResponse = await tokenRequest.GetResponseAsync();
                using (StreamReader reader = new StreamReader(tokenResponse.GetResponseStream()))
                {
                    // reads response body
                    return await reader.ReadToEndAsync();
                }
            }
            catch (WebException ex)
            {
                if (ex.Status == WebExceptionStatus.ProtocolError)
                {
                    var response = ex.Response as HttpWebResponse;
                    if (response != null)
                    {
                        Console.WriteLine("HTTP: " + response.StatusCode);
                        using (StreamReader reader = new StreamReader(response.GetResponseStream()))
                        {
                            // reads response body
                            string responseText = await reader.ReadToEndAsync();
                            Console.WriteLine(responseText);
                        }
                    }
                }

                throw ex;
            }
        }

        // Hack to bring the Console window to front.

        [DllImport("kernel32.dll", ExactSpelling = true)]
        public static extern IntPtr GetConsoleWindow();

        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool SetForegroundWindow(IntPtr hWnd);

        public void BringConsoleToFront()
        {
            SetForegroundWindow(GetConsoleWindow());
        }
    }
}

C# - Send Email Using Microsoft OAuth + Office 365 EWS Protocol in ASP.NET/ASP MVC

If you use Microsoft OAuth in ASP.NET/ASP MVC application, you should use a ASP.NET page or ASP MVC Controller to get authorization code instead of HttpListener. You need to add your ASP.NET page or ASP MVC Controller routing path to Authorized Redirect URIs in your Azure application.

// Please add http://localhost:54098/oauth/token to Authorized redirect URIs in your Google/MS Azure project.
public ActionResult Token(string code)
{
    // code parameter is the authorization code returned by Microsoft OAuth server,
    // then you can use it to request AccessToken
    // just like RequestAccessToken method in previous example
}

You can find a full sample project in EASendMail installation path\Samples_ASPNetMvc.

TLS 1.2 Protocol

TLS is the successor of SSL, more and more SMTP servers require TLS 1.2 encryption now.

If your operating system is Windows XP/Vista/Windows 7/Windows 2003/2008/2008 R2/2012/2012 R2, you need to enable TLS 1.2 protocol in your operating system like this:

Enable TLS 1.2 on Windows XP/Vista/7/10/Windows 2008/2008 R2/2012

Appendix

Comments

If you have any comments or questions about above example codes, please click here to add your comments.