asp.net core 发送QQ邮件

.netframework 中发送邮件的api主要是使用SmtpClient 类，到了.netcore,官方并不推荐使用SmtpClient API，详情可查看官方说明:https://docs.microsoft.com/en-us/dotnet/api/system.net.mail.smtpclient?view=net-5.0,因此这里我使用第三方邮件发送库：MailKit 来进行邮件的发送。

配置QQ邮箱

• 登录QQ邮箱，选择设置->账户->POP3/IMAP/SMTP/Exchange/CardDAV/CalDAV服务
  
  开启POP3/SMTP服务以及IMAP/SMTP服务。

POP3服务开启流程
1.开启POP3服务![]
(https://www.lovecoding.com.cn:99//5596824483738550145.png)

2.POP3服务开启成功后如下图所示，会弹出一个框，注意：不是用这个框里的密码进行发送邮件

3.生成用于发送邮件的授权码

IMAP服务开启流程
开启流程和POP3开启流程类似。

创建邮件发送接口

• 安装nuget包MailKit
• 添加IMailService接口

  using System;
  using System.Collections.Generic;
  using System.Text;
  using System.Threading.Tasks;
  
  namespace CommonLib.Email
  {
  	public interface IMailService
  	{
  		Task SendEmailAsync(MailRequest mailRequest);
  	}
  }
  

• 创建邮件信息相关实体类

  using Microsoft.AspNetCore.Http;
  using System;
  using System.Collections.Generic;
  using System.Text;
  namespace CommonLib.Email
  {
  	public class MailRequest
  	{
  		//收件地址
  		public string ToEmail { get; set; }
  		//邮件标题
  		public string Subject { get; set; }
  		//邮件内容,支持html
  		public string Body { get; set; }
  		//要发送的附件
  		public List<IFormFile> Attachments { get; set; }
  	}
  }
  

• 创建邮箱配置信息实体类

  using System;
  using System.Collections.Generic;
  using System.Text;
  namespace CommonLib.Email
  {
  	public class MailSettings
  	{
  		//用于发送邮件的邮箱账号
  		public string Mail { get; set; }
  		//显示名称
  		public string DisplayName { get; set; }
  		//用于发送邮件的邮箱账号的授权码
  		public string Password { get; set; }
  		//用于发送邮件的邮箱服务器,QQ邮箱是：smtp.qq.com
  		public string Host { get; set; }
  		//用于发送邮件的邮箱服务器端口,QQ邮箱的端口是25
  		public int Port { get; set; }
  	}
  }
  

• 创建实现具体邮件发送逻辑的类,并实现IMailService接口

  using MailKit.Net.Smtp;
  using MailKit.Security;
  using Microsoft.Extensions.Options;
  using MimeKit;
  using System;
  using System.Collections.Generic;
  using System.IO;
  using System.Text;
  using System.Threading.Tasks;
  namespace CommonLib.Email
  {
  	public class MailService : IMailService
  	{
  		private readonly MailSettings _mailSettings;
  		public MailService(IOptions<MailSettings> mailSettings)
  		{
  			_mailSettings = mailSettings.Value;
  			//这里这个密码是QQ邮箱授权码
  			_mailSettings.Password = mailSettings.Value.Password;
  		}
  		public async Task SendEmailAsync(MailRequest mailRequest)
  		{
  			var email = new MimeMessage();
  			//一定要使用下面这句代码添加发送人邮箱信息,否则QQ收件箱那边无法看到发送人的邮箱信息。
  			email.From.Add(MailboxAddress.Parse(_mailSettings.Mail));
  			email.Sender = MailboxAddress.Parse(_mailSettings.Mail);
  			email.To.Add(MailboxAddress.Parse(mailRequest.ToEmail));
  			email.Subject = mailRequest.Subject;
  			var builder = new BodyBuilder();
  			if (mailRequest.Attachments != null)
  			{
  				byte[] fileBytes;
  				foreach (var file in mailRequest.Attachments)
  				{
  					if (file.Length > 0)
  					{
  						using (var ms = new MemoryStream())
  						{
  							file.CopyTo(ms);
  							fileBytes = ms.ToArray();
  						}
  						builder.Attachments.Add(file.FileName, fileBytes, MimeKit.ContentType.Parse(file.ContentType));
  					}
  				}
  			}
  			builder.HtmlBody = mailRequest.Body;
  			email.Body = builder.ToMessageBody();
  			using (var smtp = new SmtpClient())
  			{
  				smtp.Connect(_mailSettings.Host, _mailSettings.Port, SecureSocketOptions.StartTls);
  				smtp.Authenticate(_mailSettings.Mail, _mailSettings.Password);
  				await smtp.SendAsync(email);
  				smtp.Disconnect(true);
  			}
  		}
  	}
  }
  

打开appsettings.Development.json文件，加入发送邮件所用到的邮箱账号、邮箱服务器等信息。

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "MailSettings": {
    "Mail": "2782815239@qq.com",
    "DisplayName": "陈新",
    "Password": "xxx",
    "Host": "smtp.qq.com",
    "Port": 25
  },
  "urls": "http://*:80"
}

到这里，基本配置工作已经完成，但是需要注意的是将代码发布到云服务器上（如腾讯云）时需要注意解封25端口，否则无法正常发送邮件。

腾讯云25端口开放方法请参见：https://cloud.tencent.com/document/product/213/40436