How can I fix email confirmation - in .NET Core, it doesn't work

Question

I already have a register action

public async Task<IActionResult> OnPostAsync(string returnUrl = null)
{
            var useremail = _userManager.Users.FirstOrDefault(u => u.Email.ToLower() == Input.Email.ToLower());

            if (useremail == null)
            {
                returnUrl = returnUrl ?? Url.Content("~/");
                ExternalLogins = (await _signInManager.GetExternalAuthenticationSchemesAsync()).ToList();

                if (ModelState.IsValid)
                {
                    var user = new IdentityUser { UserName = Input.UserName, Email = Input.Email };
                    var result = await _userManager.CreateAsync(user, Input.Password);
                    if (result.Succeeded)
                    {
                        _logger.LogInformation("User created a new account with password.");

                        var code = await _userManager.GenerateEmailConfirmationTokenAsync(user);
                        code = WebEncoders.Base64UrlEncode(Encoding.UTF8.GetBytes(code));
                        var callbackUrl = Url.Page(
                            "/Account/ConfirmEmail",
                            pageHandler: null,
                            values: new { area = "Identity", userId = user.Id, code = code },
                            protocol: Request.Scheme);

                        await _emailSender.SendEmailAsync(Input.Email, "Confirm your email",
                            $"Please confirm your account by <a href='{HtmlEncoder.Default.Encode(callbackUrl)}'>clicking here</a>.");

                        if (_userManager.Options.SignIn.RequireConfirmedAccount)
                        {
                            return RedirectToPage("RegisterConfirmation", new { email = Input.Email });
                        }
                        else
                        {
                            await _signInManager.SignInAsync(user, isPersistent: false);
                            return LocalRedirect(returnUrl);
                        }
                    }

                    foreach (var error in result.Errors)
                    {
                        ModelState.AddModelError(string.Empty, error.Description);
                    }
                }
            }
            // If we got this far, something failed, redisplay form
            ViewData["EmailExists"] = "Try another email that one is used";

            return Page();
}

Then I created the sendgrid user and key and registered them by CMD, then I created the action of send email

public class EmailSender : IEmailSender
{
        public EmailSender(IOptions<AuthMessageSenderOptions>optionsAccessor)
        {
            Options = optionsAccessor.Value;
        }

        public AuthMessageSenderOptions Options { get; }

        public Task SendEmailAsync (string email , string subject , string message)
        {
            return Excute(Options.SendGridKey,subject,message,email);
        }

        private Task Excute(string apiKey, string subject, string message, string email)
        {
            var client = new SendGridClient(apiKey);
            var msg = new SendGridMessage()
            {
                From = new EmailAddress("[email protected]", "dary dress"),
                Subject = subject,
                PlainTextContent = message,
                HtmlContent = message
            };

            msg.AddTo(new EmailAddress(email));
            msg.SetClickTracking(false, false);

            return client.SendEmailAsync(msg);
        }
}

Then in startup.cs

public IConfiguration Configuration { get; }

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<ApplicationDbContext>(options =>
          options.UseSqlServer(
                    Configuration.GetConnectionString("DefaultConnection")));
    services.AddIdentity<IdentityUser, IdentityRole>( options => options.SignIn.RequireConfirmedAccount = true)
                .AddDefaultUI()
                .AddDefaultTokenProviders()
                .AddEntityFrameworkStores<ApplicationDbContext>();
    services.AddControllersWithViews();
    services.AddRazorPages();
    services.AddMvc();
    services.AddTransient<IEmailSender, EmailSender>();
    services.Configure<AuthMessageSenderOptions>(Configuration);
    services.AddPaging();
    services.ConfigureApplicationCookie(o => {
                o.ExpireTimeSpan = TimeSpan.FromDays(5);
                o.SlidingExpiration = true;
            });
    services.AddMvc(options =>
            {
                options.Filters.Add(new RequireHttpsAttribute());
            });
    services.ConfigureApplicationCookie(options =>
            {
                options.AccessDeniedPath = new Microsoft.AspNetCore.Http.PathString("/Main/AccessDenied");
            });
}

but sending an e-mail doesn't work after registration gives me some words that i need confirm my email and gives me link to confirm my email but doesn't send it to gmail

Does anyone have an idea?

I followed this documentation from microsoft https://learn.microsoft.com/en-us/aspnet/core/security/authentication/accconfirm?view=aspnetcore-3.1&tabs=visual-studio

Answer 1

"Solved" I asked Sendgrid, and I was told that I cannot use my yahoo email (or gmail,...) as the sender email; this is part of the answer: "Yahoo observes an email security standard called DMARC. DMARC instructs email providers to reject messages where the From domain is a Yahoo domain, but the message originates from a non-approved domain server/service." So I need to use my own mail domain;