OAuth 2.0 device flow with Office365/Exchange IMAP/POP3/SMTP

string clientId = "Application (client) ID";
string tenantId = "Directory (tenant) ID";

IPublicClientApplication app = PublicClientApplicationBuilder
    .Create(clientId)
    .WithTenantId(tenantId)
    .Build();
// This allows saving access/refresh tokens to some storage
TokenCacheHelper.EnableSerialization(app.UserTokenCache);

var scopes = new string[] 
{
    "offline_access",
    "email",
    "https://outlook.office.com/IMAP.AccessAsUser.All",
    "https://outlook.office.com/POP.AccessAsUser.All",
    "https://outlook.office.com/SMTP.Send",
};

string userName;
string accessToken;

var account = (await app.GetAccountsAsync()).FirstOrDefault();
try
{
    AuthenticationResult refresh = await app
        .AcquireTokenSilent(scopes, account)
        .ExecuteAsync();

    userName = refresh.Account.Username;
    accessToken = refresh.AccessToken;
}
catch (MsalUiRequiredException e)
{
    var acquire = await app.AcquireTokenWithDeviceCode(
        scopes, 
        callback=>
    {
        // Write url and code to logs so the operator can react:
        Console.WriteLine(callback.VerificationUrl);
        Console.WriteLine(callback.UserCode);

        // This happens on the first run, manually,
        //  on the operator machine.
        // The code below code is only to illustrate 
        // the operator opening browser on his machine,
        // opening the url and using the code 
        // (extracted from the application logs)
        // to authenticate the app.
        System.Diagnostics.Process.Start(
            new ProcessStartInfo(result.VerificationUrl) 
                        { UseShellExecute = true }
            );

        return Task.CompletedTask;
    }).ExecuteAsync();

    userName = acquire.Account.Username;
    accessToken = acquire.AccessToken;
}

using (Imap client = new Imap())
{
    client.ConnectSSL("outlook.office365.com");
    client.LoginOAUTH2(userName, accessToken);
 
    client.SelectInbox();

    // ...

    client.Close();
} 

static class TokenCacheHelper
{
    public static void EnableSerialization(ITokenCache tokenCache)
    {
        tokenCache.SetBeforeAccess(BeforeAccessNotification);
        tokenCache.SetAfterAccess(AfterAccessNotification);
    }

    private static readonly string _fileName = "msalcache.bin3";

    private static readonly object _fileLock = new object();


    private static void BeforeAccessNotification(TokenCacheNotificationArgs args)
    {
        lock (_fileLock)
        {
            byte[] data = null;
            if (File.Exists(_fileName))
                data = File.ReadAllBytes(_fileName);
            args.TokenCache.DeserializeMsalV3(data);
        }
    }

    private static void AfterAccessNotification(TokenCacheNotificationArgs args)
    {
        if (args.HasStateChanged)
        {
            lock (_fileLock)
            {
                byte[] data = args.TokenCache.SerializeMsalV3();
                File.WriteAllBytes(_fileName, data);
            }
        }
    }
};