var message = new MimeMessage ();
message.From.Add (new MailboxAddress ("Joey Tribbiani", "joey@friends.com"));
message.To.Add (new MailboxAddress ("Mrs. Chanandler Bong", "chandler@friends.com"));

message.Subject = "星期天去哪里玩？";

message.Body = new TextPart ("plain") { Text = "我想去故宫玩，如何" };

using (var client = new SmtpClient ()) {
  // For demo-purposes, accept all SSL certificates (in case the server supports STARTTLS)
  client.ServerCertificateValidationCallback = (s,c,h,e) => true;

  client.Connect ("smtp.friends.com", 587, false);

  // Note: since we don't have an OAuth2 token, disable
  // the XOAUTH2 authentication mechanism.
  client.AuthenticationMechanisms.Remove ("XOAUTH2");

  // Note: only needed if the SMTP server requires authentication
  client.Authenticate ("joey", "password");

  client.Send (message);
  client.Disconnect (true);
}

var bodyBuilder = new BodyBuilder();
bodyBuilder.HtmlBody = @"<b>This is bold and this is <i>italic</i></b>";
message.Body = bodyBuilder.ToMessageBody();

Install-Package FluentEmail.Razor

//注意： .NET 4.6 才支持
Email.DefaultSender = new SmtpSender();

var email = Email
  .From("foo@email.com")
  .To("bar@email.com", "bob")
  .Subject("星期天去哪里玩？")
  .Body("我想去故宫玩，如何？");

await email.SendAsync();

//注意： .NET 4.6 才支持
Email.DefaultSender = new SmtpSender();

// Using Razor templating package
Email.DefaultRenderer = new RazorRenderer();

var template = "Dear @Model.Name, You are totally @Model.Compliment.";

var email = Email
  .From("bob@hotmail.com")
  .To("somedude@gmail.com")
  .Subject("woo nuget")
  .UsingTemplate(template, new { Name = "Luke", Compliment = "Awesome" });

//注意： .NET 4.6 才支持
Email.DefaultSender = new SmtpSender();

Email.DefaultRenderer = new RazorRenderer();

var email = Email
  .From("foo@email.com")
  .To("bar@email.com", "bob")
  .Subject("星期天去哪里玩？")
  .UsingTemplateFromFile($"{Directory.GetCurrentDirectory}/EmailTemplage.cshtml", new {Name ="Luke"})

Install-Package FluentEmail.Mailgun

// 同时支持 .NET Core 和 .NET Framework
var sender = new MailgunSender(
  "sandboxcf5f41bbf2f84f15a386c60e253b5fe8.mailgun.org", // Mailgun 二级域名
  "key-8d32c046d7f14ada8d5ba8253e3e30df" // Mailgun API Key
);

Email.DefaultSender = sender;

var email = Email
  .From("foo@email.com")
  .To("bar@email.com", "bob")
  .Subject("星期天去哪里玩？")
  .Body("我想去故宫玩，如何？");

await email.SendAsync();