網上找了一下，發現一個很不錯的郵件傳送服務Mailgun，首先要註冊Mailgun賬號，獲得apikey以及domainame；

　　然後專案中安裝nuget：

　　配置並註冊服務：

　　public interface IEmailSender
    {
        Task SendEmailAsync(string email, string subject, string message);
    }

　　public class EmailSender:IEmailSender
    {
        private readonly
 
 EmailSettings _emailSettings;

        public EmailSender(IOptions<EmailSettings> emailOptions)
        {
            _emailSettings = emailOptions.Value;
        }

        public Task SendEmailAsync(string account, string subject, string mess)
        {
            var domainName = _emailSettings.DomainName;
            
 
var apiKey = _emailSettings.ApiKey;
            var sender = new MailgunSender(domainName, apiKey);
            Email.DefaultSender = sender;
            var email = Email.From(_emailSettings.From, "XXXXXXX平臺")
                .To(account)
                .Subject(subject)
                .Body(mess);
            
 
return email.SendAsync();
        }
    }

　　public class EmailSettings
    {
        public string ApiKey { get; set; }
        public string ApiBaseUri { get; set; }
        public string RequestUri { get; set; }
        public string From { get; set; }
        public  string DomainName { get; set; }
    }

 　　　　　　　#region 註冊郵件服務
            services.Configure<EmailSettings>(Configuration.GetSection("EmailSettings"));
            services.AddTransient<IEmailSender, EmailSender>();
            #endregion

　　呼叫：

　　public class TestController : Controller
    {
        private readonly IOptions<EmailSettings> _emailOptions;
        private readonly ILogger<TestController> _logger;
        private readonly IEmailSender _emailSender;

        public TestController(IOptions<EmailSettings> emailOptions,ILogger<TestController> logger,IEmailSender emailSender)
        {
            _emailOptions = emailOptions;
            _logger = logger;
            _emailSender = emailSender;
        }
        public async Task<IActionResult> Index()
        {
            try
            {
                string code = "259878";
                await _emailSender.SendEmailAsync("[email protected]",EmailType.Captcha ,$"驗證碼：{code}，如非本人操作請忽略。");
                _logger.LogInformation("傳送郵件，to："+"[email protected]"+",型別："+EmailType.Captcha);
                return Content("ok");
            }
            catch (Exception e)
            {
                return Content("出錯了："+e.Message);
            }
            
        }
    }

　　收到驗證碼：