C#通过Gmail编程发送电子邮件

using Google.Apis.Auth.OAuth2;
using Google.Apis.Gmail.v1;
using Google.Apis.Gmail.v1.Data;
using Google.Apis.Services;
using Google.Apis.Util.Store;
using System;
using System.IO;
using System.Threading;

namespace GmailAPISample
{
    class Program
    {
        static string[] Scopes = { GmailService.Scope.GmailCompose, GmailService.Scope.GmailSend };
        static string ApplicationName = "Gmail API C# Sample";

        static void Main(string[] args)
        {
            UserCredential credential;

            using (var stream = new FileStream("credentials.json", FileMode.Open, FileAccess.Read))
            {
                string credPath = "token.json";
                credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                    GoogleClientSecrets.Load(stream).Secrets,
                    Scopes,
                    "user",
                    CancellationToken.None,
                    new FileDataStore(credPath, true)).Result;
                Console.WriteLine("Credential file saved to: " + credPath);
            }

            var service = new GmailService(new BaseClientService.Initializer()
            {
                HttpClientInitializer = credential,
                ApplicationName = ApplicationName,
            });

            var email = CreateEmail("sender@gmail.com", "recipient@gmail.com", "Test Subject", "Test Body");
            SendEmail(service, "me", email);

            Console.WriteLine("Email sent!");
        }

        public static Message CreateEmail(string sender, string recipient, string subject, string body)
        {
            var email = new MimeKit.MimeMessage();
            email.From.Add(new MimeKit.MailboxAddress("", sender));
            email.To.Add(new MimeKit.MailboxAddress("", recipient));
            email.Subject = subject;
            email.Body = new MimeKit.TextPart("plain")
            {
                Text = body
            };

            using (var stream = new MemoryStream())
            {
                email.WriteTo(stream);
                return new Message
                {
                    Raw = Convert.ToBase64String(stream.ToArray())
                };
            }
        }

        public static void SendEmail(GmailService service, string userId, Message email)
        {
            service.Users.Messages.Send(email, userId).Execute();
        }
    }
}