Managed C++/CLI - Send email using Microsoft OAuth 2.0 (Modern Authentication) + SMTP/EWS protocol from Office 365 account

You can send email using traditional user/password authentication from Office 365 account by SMTP/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 Azure Portal.

  • 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

Single tenant and multitenant in account type

When the register an application page appears, enter a meaningful application name and select the account type.

Select which accounts you would like your application to support.

  • If your application only supports the users in your directory or organization, please select Single tenant type;
  • If your application needs to support all users in Office 365 and Microsoft personal account (hotmail.com, outlook.com), please select Multitenant type, and you must verify publisher.

Because we want to support all Office 365 and LIVE SDK (hotmail, outlook personal account), so select Accounts in any organizational directory and personal Microsoft accounts.

Important

If you don’t verify publisher for multitenant application, your application will not request access token successfully.

API permission

Now we need to add permission to the application:

  • Click API Permission ->
  • Add a permission -> Microsoft Graph -> Delegated Permission -> User.Read, email, offline_access, openid, profile, SMTP.Send, IMAP.AccessAsUser.All, POP.AccessAsUser.All.
azure application SMTP/POP/IMAP api permission

EWS API permission

With the above permissions, your application can support SMTP, POP and IMAP service. If your application needs to support EWS protocol either, add EWS permission like this:

  • Click API Permission ->
  • Add a permission -> APIs in my organization uses -> Office 365 Exchange Online -> Delegated Permission -> Check EWS.AccessAsUser.All
azure APIs in my organization uses

Here is permissions list:

azure application api permission list

Authentication and redirect uri

Because the example code is based on desktop application, so add Redirect Uri like this:

  • Click "Authentication" -> Add a platform -> 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.
  • If your application needs to support Microsoft personal account, set both "Live SDK Support" and "Treat application as a public client" to "Yes".

azure application Authentication Overview

Client Id and client secrets

Now we need to create a client secret for the application, click Certificates and secrets -> client secrets and add a new client secret.

azure application api permission

After client secret is created, store the client secret value to somewhere.

Important

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

Branding and verify publisher

Now we click Branding, you can edit your company logo, URL and application name. If your application supports multitenant (access user in all Office 365 and Microsoft personal account), you must complete the publisher verification.

It is not difficult, you can have a look at publisher verification. After publisher verification is completed, your branding is like this:

azure application Authentication Overview

Important

You must complete the publisher verification for multitenant application, otherwise, your application will not request access token correctly.

Client id and tenant

Now you can click Overview to find your client id and tenant.

azure application client id and tenant
  • If your application is single tenant, use the tenant value in tokenUri and authUri instead of common.
  • If your application is multitenant, use common as tenant.

Above client id and client secret support both "Office365 + SMTP/EWS" and "Live (hotmail, outlook personal account) + SMTP",

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 Oauth Url;
  • User inputs user and password in web authentication page, and then the Oauth server returns access token back to your application;
  • Your application uses access token to access resource on the server.
  • You can find full example codes in EASendMail Installation Path\Samples_{Programming language/Developer Tool}\Oauth project.

Access token expiration and refresh token

You don’t have to open browser to request access token every time. By default, access token expiration time is 3600 seconds, you can use the access token repeatedly before it is expired. After it is expired, you can use refresh token to refresh access token directly without opening browser. You can find full sample project in EASendMail installation path to learn how to refresh token.

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.

Managed C++/CLI - Send email using Microsoft OAuth + Office 365 SMTP protocol

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

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.

#include "stdafx.h"
using namespace System;
using namespace System::IO;
using namespace System::Net;
using namespace System::Net::Sockets;
using namespace System::Text;
using namespace System::Threading;
using namespace System::Threading::Tasks;
using namespace System::Runtime::InteropServices;
using namespace EASendMail;

// Hack to bring the Console window to front.
[DllImport("kernel32.dll", CharSet = CharSet::Ansi)]
extern "C" void* GetConsoleWindow();

[DllImport("user32.dll", CharSet = CharSet::Ansi)]
extern "C" Int32 SetForegroundWindow(void* hWnd);

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

ref class MsOauthOffice365
{


public:
    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.
        auto http = gcnew 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.
        auto asyncResult = http->BeginGetContext(nullptr, nullptr);
        while (!asyncResult->AsyncWaitHandle->WaitOne(10))
        {
        }

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

        auto context = http->EndGetContext(asyncResult);

        // Sends an HTTP response to the browser.
        auto response = context->Response;
        String^ responseString = "<html><head></head><body>Please return to the app and close current window.</body></html>";
        auto buffer = Encoding::UTF8->GetBytes(responseString);
        response->ContentLength64 = buffer->Length;

        auto responseOutput = response->OutputStream;
        responseOutput->Write(buffer, 0, buffer->Length);
        responseOutput->Close();
        http->Stop();
        Console::WriteLine("HTTP server stopped.");

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

        if (context->Request->QueryString->Get("code") == nullptr)
        {
            Console::WriteLine("Malformed authorization response. " + context->Request->RawUrl);
            return;
        }

        // extracts the code
        auto code = context->Request->QueryString->Get("code");
        Console::WriteLine("Authorization code: " + code);

        String^ responseText = RequestAccessToken(code, redirectUri);
        Console::WriteLine(responseText);

        OAuthResponseParser^ parser = gcnew OAuthResponseParser();
        parser->Load(responseText);

        auto user = parser->EmailInIdToken;
        auto accessToken = parser->AccessToken;

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

        SendMailWithXOAUTH2(user, accessToken);
    }

private:
    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
        auto 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";

        auto _byteVersion = Encoding::ASCII->GetBytes(tokenRequestBody);
        tokenRequest->ContentLength = _byteVersion->Length;

        Stream^ stream = tokenRequest->GetRequestStream();
        stream->Write(_byteVersion, 0, _byteVersion->Length);
        stream->Close();

        try
        {
            // gets the response
            auto tokenResponse = tokenRequest->GetResponse();

            {
                StreamReader^ reader = gcnew StreamReader(tokenResponse->GetResponseStream());
                // reads response body
                return reader->ReadToEnd();
            }

        }
        catch (WebException ^ex)
        {
            if (ex->Status == WebExceptionStatus::ProtocolError)
            {
                auto response = (HttpWebResponse^)ex->Response;
                if (response != nullptr)
                {
                    Console::WriteLine("HTTP: " + response->StatusCode.ToString());

                    {
                        StreamReader^ reader = gcnew StreamReader(response->GetResponseStream());
                        // reads response body
                        Console::WriteLine(reader->ReadToEnd());
                    }
                }
            }

            throw ex;
        }
    }

    void SendMailWithXOAUTH2(String^ userEmail, String^ accessToken)
    {
        // Office365 server address
        SmtpServer ^oServer = gcnew SmtpServer("outlook.office365.com");
        // Using 587 port, you can also use 465 port
        oServer->Port = 587;
        // 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 = gcnew SmtpMail("TryIt");
        // Your email address
        oMail->From = userEmail;

        // Please change recipient address to yours for test
        oMail->To = gcnew String("support@emailarchitect.net");

        oMail->Subject = "test email from Office365 account with OAUTH 2";
        oMail->TextBody = "this is a test email sent from C++/CLR project with Office365.";

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

        SmtpClient ^oSmtp = gcnew 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.
    String^ clientID = "eccbabb2-3377-4265-85c1-ea2fb515f075";
    String^ clientSecret = "QaR_RR:-5WqTY[nni9pdBr9xVybqrAu4";
    // set SMTP scope
    String^ scope = "https://outlook.office.com/SMTP.Send%20offline_access%20email%20openid";
    String^ authUri = "https://login.microsoftonline.com/common/oauth2/v2.0/authorize";
    String^ tokenUri = "https://login.microsoftonline.com/common/oauth2/v2.0/token";

    // if your application is single tenant, please use tenant id instead of common in authUri and tokenUri
    // for example, your tenant is 669595d0-a4d7-47c5-8040-cf9970400e48, then
    // String^ authUri = "https://login.microsoftonline.com/669595d0-a4d7-47c5-8040-cf9970400e48/oauth2/v2.0/authorize";
    // String^ tokenUri = "https://login.microsoftonline.com/669595d0-a4d7-47c5-8040-cf9970400e48/oauth2/v2.0/token";

    // ref http://stackoverflow.com/a/3978040
    static int GetRandomUnusedPort()
    {
        auto listener = gcnew TcpListener(IPAddress::Loopback, 0);
        listener->Start();
        auto port = ((IPEndPoint^)listener->LocalEndpoint)->Port;
        listener->Stop();
        return port;
    }
};

int main(array<System::String ^> ^args)
{
    Console::WriteLine("+------------------------------------------------------------------+");
    Console::WriteLine("  Sign in with Microsoft 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
    {
        MsOauthOffice365^ p = gcnew MsOauthOffice365();
        p->DoOauthAndSendEmail();
    }
    catch (Exception ^ep)
    {
        Console::WriteLine(ep->ToString());
    }

    Console::ReadKey();

    return 0;
}

Managed C++/CLI - 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 with EWS protocol.

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.

#include "stdafx.h"
using namespace System;
using namespace System::IO;
using namespace System::Net;
using namespace System::Net::Sockets;
using namespace System::Text;
using namespace System::Threading;
using namespace System::Threading::Tasks;
using namespace System::Runtime::InteropServices;
using namespace EASendMail;

// Hack to bring the Console window to front.
[DllImport("kernel32.dll", CharSet = CharSet::Ansi)]
extern "C" void* GetConsoleWindow();

[DllImport("user32.dll", CharSet = CharSet::Ansi)]
extern "C" Int32 SetForegroundWindow(void* hWnd);

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

ref class MsOauthOffice365
{


public:
    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.
        auto http = gcnew 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.
        auto asyncResult = http->BeginGetContext(nullptr, nullptr);
        while (!asyncResult->AsyncWaitHandle->WaitOne(10))
        {
        }

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

        auto context = http->EndGetContext(asyncResult);

        // Sends an HTTP response to the browser.
        auto response = context->Response;
        String^ responseString = "<html><head></head><body>Please return to the app and close current window.</body></html>";
        auto buffer = Encoding::UTF8->GetBytes(responseString);
        response->ContentLength64 = buffer->Length;

        auto responseOutput = response->OutputStream;
        responseOutput->Write(buffer, 0, buffer->Length);
        responseOutput->Close();
        http->Stop();
        Console::WriteLine("HTTP server stopped.");

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

        if (context->Request->QueryString->Get("code") == nullptr)
        {
            Console::WriteLine("Malformed authorization response. " + context->Request->RawUrl);
            return;
        }

        // extracts the code
        auto code = context->Request->QueryString->Get("code");
        Console::WriteLine("Authorization code: " + code);

        String^ responseText = RequestAccessToken(code, redirectUri);
        Console::WriteLine(responseText);

        OAuthResponseParser^ parser = gcnew OAuthResponseParser();
        parser->Load(responseText);

        auto user = parser->EmailInIdToken;
        auto accessToken = parser->AccessToken;

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

        SendMailWithXOAUTH2(user, accessToken);
    }

private:
    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
        auto 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";

        auto _byteVersion = Encoding::ASCII->GetBytes(tokenRequestBody);
        tokenRequest->ContentLength = _byteVersion->Length;

        Stream^ stream = tokenRequest->GetRequestStream();
        stream->Write(_byteVersion, 0, _byteVersion->Length);
        stream->Close();

        try
        {
            // gets the response
            auto tokenResponse = tokenRequest->GetResponse();

            {
                StreamReader^ reader = gcnew StreamReader(tokenResponse->GetResponseStream());
                // reads response body
                return reader->ReadToEnd();
            }

        }
        catch (WebException ^ex)
        {
            if (ex->Status == WebExceptionStatus::ProtocolError)
            {
                auto response = (HttpWebResponse^)ex->Response;
                if (response != nullptr)
                {
                    Console::WriteLine("HTTP: " + response->StatusCode.ToString());

                    {
                        StreamReader^ reader = gcnew StreamReader(response->GetResponseStream());
                        // reads response body
                        Console::WriteLine(reader->ReadToEnd());
                    }
                }
            }

            throw ex;
        }
    }

    void SendMailWithXOAUTH2(String^ userEmail, String^ accessToken)
    {
        // Office365 server address
        SmtpServer ^oServer = gcnew 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 = gcnew SmtpMail("TryIt");
        // Your email address
        oMail->From = userEmail;

        // Please change recipient address to yours for test
        oMail->To = gcnew String("support@emailarchitect.net");

        oMail->Subject = "test email from Office365 account with OAUTH 2";
        oMail->TextBody = "this is a test email sent from C++/CLR project with Office365.";

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

        SmtpClient ^oSmtp = gcnew 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.
    String^ clientID = "eccbabb2-3377-4265-85c1-ea2fb515f075";
    String^ clientSecret = "QaR_RR:-5WqTY[nni9pdBr9xVybqrAu4";
    // set EWS scope
    String^ scope = "https://outlook.office.com/EWS.AccessAsUser.All%20offline_access%20email%20openid";
    String^ authUri = "https://login.microsoftonline.com/common/oauth2/v2.0/authorize";
    String^ tokenUri = "https://login.microsoftonline.com/common/oauth2/v2.0/token";

    // if your application is single tenant, please use tenant id instead of common in authUri and tokenUri
    // for example, your tenant is 669595d0-a4d7-47c5-8040-cf9970400e48, then
    // String^ authUri = "https://login.microsoftonline.com/669595d0-a4d7-47c5-8040-cf9970400e48/oauth2/v2.0/authorize";
    // String^ tokenUri = "https://login.microsoftonline.com/669595d0-a4d7-47c5-8040-cf9970400e48/oauth2/v2.0/token";

    // ref http://stackoverflow.com/a/3978040
    static int GetRandomUnusedPort()
    {
        auto listener = gcnew TcpListener(IPAddress::Loopback, 0);
        listener->Start();
        auto port = ((IPEndPoint^)listener->LocalEndpoint)->Port;
        listener->Stop();
        return port;
    }
};

int main(array<System::String ^> ^args)
{
    Console::WriteLine("+------------------------------------------------------------------+");
    Console::WriteLine("  Sign in with Microsoft 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
    {
        MsOauthOffice365^ p = gcnew MsOauthOffice365();
        p->DoOauthAndSendEmail();
    }
    catch (Exception ^ep)
    {
        Console::WriteLine(ep->ToString());
    }

    Console::ReadKey();

    return 0;
}

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

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