SocketException：尚无此类主机

Question

在基于ASP.NET Core 1.1.1开发的VS2017 Ver 15.3.3应用中，我正在使用Account confirmation and password recovery in ASP.NET Core和MailKit来实现上述文章的功能，但出现以下错误：

注：

1. 错误在下面的await client.ConnectAsync("smtp.relay.uri", 25, SecureSocketOptions.None).ConfigureAwait(false);方法的第SendEmailAsync(...)行出现，并且
2. await _emailSender.SendEmailAsync(model.Email, "Confirm your account", $"Please confirm your account by clicking this link: <a href='{callbackUrl}'>link</a>");发布方法的Register(...)行也如下所示：

ERROR

SocketException：尚无此类主机

MessageServices.cs类

public class AuthMessageSender : IEmailSender, ISmsSender
{
    public async Task SendEmailAsync(string email, string subject, string message)
    {
        // Plug in your email service here to send an email.
        //return Task.FromResult(0);
        var emailMessage = new MimeMessage();

        //You can if required (and I have done in my code) set the LocalDomain used when communicating with the SMTP server
        //This will be presented as the origin of the emails. In my case I needed to supply the domain so that our internal testing SMTP server would accept and relay my emails.
        //We then asynchronously connect to the SMTP server. The ConnectAsync method can take just the uri of the SMTP server or as I’ve done here be overloaded with a port and SSL option. For my case when testing with our local test SMTP server no SSL was required so I specified this explicitly to make it work.
        emailMessage.From.Add(new MailboxAddress("MyName", "[email protected]"));
        emailMessage.To.Add(new MailboxAddress("", email));
        emailMessage.Subject = subject;
        emailMessage.Body = new TextPart("plain") { Text = message };

        using (var client = new SmtpClient())
        {
            client.LocalDomain = "smtp.MyDomain.com";
            await client.ConnectAsync("smtp.relay.uri", 25, SecureSocketOptions.None).ConfigureAwait(false);
            await client.SendAsync(emailMessage).ConfigureAwait(false);
            await client.DisconnectAsync(true).ConfigureAwait(false);
        }
    }

在AccountController.cs中注册发布方法

[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Register(RegisterViewModel model, string returnUrl = null)
{
    ViewData["ReturnUrl"] = returnUrl;
    if (ModelState.IsValid)
    {
        var user = new ApplicationUser { UserName = model.Email, Email = model.Email };
        var result = await _userManager.CreateAsync(user, model.Password);
        if (result.Succeeded)
        {
            // For more information on how to enable account confirmation and password reset please visit https://go.microsoft.com/fwlink/?LinkID=532713
            // Send an email with this link
            var code = await _userManager.GenerateEmailConfirmationTokenAsync(user);
            var callbackUrl = Url.Action(nameof(ConfirmEmail), "Account", new { userId = user.Id, code = code }, protocol: HttpContext.Request.Scheme);
            await _emailSender.SendEmailAsync(model.Email, "Confirm your account",
                $"Please confirm your account by clicking this link: <a href='{callbackUrl}'>link</a>");
            await _signInManager.SignInAsync(user, isPersistent: false);
            _logger.LogInformation(3, "User created a new account with password.");
            return RedirectToLocal(returnUrl);
        }
        AddErrors(result);
    }

UPDATE

不确定，但是错误可能与我没有正确使用我的电子邮件主机信息有关：

1. 我正在使用网站/电子邮件托管公司DiscountASP.NET的网络邮件功能。每个订户的SMTP服务器名称为smtp.YourDomainName.com。因此，在上面的SendEmailAsync(...)方法中，我使用的是client.LocalDomain = "smtp.MyDomain.com";
2. 对于MailKit实现，我正在关注Sending email via a SMTP server文章的this部分。

Answer 1

打开您的cmd并在Windows上编写ipconfig / all，然后搜索您的PC主机名 alt =”然后在此功能中输入您的主机名