c#实现邮件发送，在百度上也有其他很多资料，但是有些不够详细，我仅仅只作为补充。我个人是使用一个静态类实现邮件的发送功能，非常简单，导入之后之需要调用即可。

首先需要设置参数值，以qq邮箱为例：打开设置》账户

往下拉，打开以下功能：生成授权码，等下有用。

网易的也类似，找到设置》基础设置》打开pops/smtp服务。同时也会获取一个授权码。拿到授权码之后。导入这个静态类，并确保能正常引用

using System;
using System.Net;
using System.Net.Mail;
using System.Text;

namespace RIM
{

	/// <summary>
	/// 软件的邮箱类，用于发送邮箱数据
	/// </summary>
	public class SoftMail
	{
		public static SoftMail MailSystem163 = new SoftMail(
		   mail =>
		   {
			   mail.Host = "smtp.163.com";//使用163的SMTP服务器发送邮件
			   //mail.UseDefaultCredentials = true;//在winform平台使用默认值
			   mail.EnableSsl = true;
			   mail.UseDefaultCredentials = false;//在.framework或mvc下使用这个
			   mail.Port = 25;//端口号
			   mail.DeliveryMethod = SmtpDeliveryMethod.Network;
			   mail.Credentials = new System.Net.NetworkCredential("邮件发送地址（自己的邮件号）如1234656@qq.com", "刚才获取的授权码");
		   },
		   "邮件发送地址（自己的邮件号）如1234656@qq.com",
		   "邮件发送地址（自己的邮件号）如1234656@qq.com"
	   );
		/// <summary>
		/// 系统连续发送失败的次数，为了不影响系统，连续三次失败就禁止发送
		/// </summary>
		private static long SoftMailSendFailedCount { get; set; } = 0L;


		/// <summary>
		/// 系统的邮件发送客户端
		/// </summary>
		private SmtpClient smtpClient { get; set; }

		/// <summary>
		/// 发送邮件的地址
		/// </summary>
		private string MailFromAddress { get; set; } = "";


		/// <summary>
		/// 邮件发送的地址
		/// </summary>
		public string MailSendAddress { get; set; } = "";


		/// <summary>
		/// 实例化一个邮箱发送类，需要指定初始化信息
		/// </summary>
		/// <param name="mailIni">初始化的方法</param>
		/// <param name="addr_From">发送地址，应该和账户匹配</param>
		/// <param name="addr_to">邮件接收地址</param>
		/// <remarks>
		/// </remarks>
		public SoftMail(Action<SmtpClient> mailIni, string addr_From = "", string addr_to = "")
		{
			smtpClient = new SmtpClient();
			mailIni(smtpClient);
			MailFromAddress = addr_From;
			MailSendAddress = addr_to;
		}

		private string GetExceptionMail(Exception ex)
		{
			return ex.Message;
		}

		/// <summary>
		/// 发生BUG至邮件地址，需要提前指定发送地址，否则失败
		/// </summary>
		/// <param name="ex">异常的BUG，同样试用兼容类型</param>
		/// <returns>是否发送成功，内容不正确会被视为垃圾邮件</returns>
		public bool SendMail(Exception ex)
		{
			return SendMail(ex, "");
		}

		/// <summary>
		/// 发送邮件至地址，需要提前指定发送地址，否则失败
		/// </summary>
		/// <param name="subject">邮件主题</param>
		/// <param name="body">邮件内容</param>
		/// <returns>是否发送成功，内容不正确会被视为垃圾邮件</returns>
		public bool SendMail(string subject, string body)
		{
			return SendMail(MailSendAddress, subject, body);
		}

		/// <summary>
		/// 发送邮件至地址，需要提前指定发送地址，否则失败
		/// </summary>
		/// <param name="subject">邮件主题</param>
		/// <param name="body">邮件内容</param>
		/// <param name="isHtml">是否是html格式化文本</param>
		/// <returns>是否发送成功，内容不正确会被视为垃圾邮件</returns>
		public bool SendMail(string subject, string body, bool isHtml)
		{
			return SendMail(MailSendAddress, subject, body, isHtml);
		}

		/// <summary>
		/// 发生BUG至邮件地址，需要提前指定发送地址，否则失败
		/// </summary>
		/// <param name="ex">异常的BUG，同样试用兼容类型</param>
		/// <param name="addtion">额外信息</param>
		/// <returns>是否发送成功，内容不正确会被视为垃圾邮件</returns>
		public bool SendMail(Exception ex, string addtion)
		{
			if (string.IsNullOrEmpty(MailSendAddress))
			{
				return false;
			}
			return SendMail(MailSendAddress, "", string.IsNullOrEmpty(addtion) ? GetExceptionMail(ex) : ("User：" + addtion + Environment.NewLine + GetExceptionMail(ex)));
		}

		/// <summary>
		/// 发送邮件的方法，需要指定接收地址，主题及内容
		/// </summary>
		/// <param name="addr_to">接收地址</param>
		/// <param name="subject">邮件主题</param>
		/// <param name="body">邮件内容</param>
		/// <returns>是否发送成功，内容不正确会被视为垃圾邮件</returns>
		public bool SendMail(string addr_to, string subject, string body)
		{
			return SendMail(addr_to, subject, body, isHtml: false);
		}

		/// <summary>
		/// 发送邮件的方法，默认发送别名，优先级，是否HTML
		/// </summary>
		/// <param name="addr_to">接收地址</param>
		/// <param name="subject">邮件主题</param>
		/// <param name="body">邮件内容</param>
		/// <param name="isHtml">是否是html格式的内容</param>
		/// <returns>是否发送成功，内容不正确会被视为垃圾邮件</returns>
		public bool SendMail(string addr_to, string subject, string body, bool isHtml)
		{
			return SendMail(MailFromAddress, "", new string[1] { addr_to }, subject, body, MailPriority.Normal, isHtml);
		}

		/// <summary>
		/// 发送邮件的方法，需要提供完整的参数信息
		/// </summary>
		/// <param name="addr_from">发送地址</param>
		/// <param name="name">发送别名</param>
		/// <param name="addr_to">接收地址</param>
		/// <param name="subject">邮件主题</param>
		/// <param name="body">邮件内容</param>
		/// <param name="priority">优先级</param>
		/// <param name="isHtml">邮件内容是否是HTML语言</param>
		/// <returns>发生是否成功，内容不正确会被视为垃圾邮件</returns>
		public bool SendMail(string addr_from, string name, string[] addr_to, string subject, string body, MailPriority priority, bool isHtml)
		{
			if (SoftMailSendFailedCount > 10)
			{
				SoftMailSendFailedCount++;
				return true;
			}
			MailMessage mailMessage = new MailMessage();
			try
			{
				mailMessage.From = new MailAddress(addr_from, name, Encoding.UTF8);
				foreach (string addresses in addr_to)
				{
					mailMessage.To.Add(addresses);
				}
				mailMessage.Subject = subject;
				mailMessage.Body = body;
				MailMessage mailMessage2 = mailMessage;
				mailMessage2.Body = mailMessage2.Body + Environment.NewLine + Environment.NewLine + Environment.NewLine;
				mailMessage.SubjectEncoding = Encoding.UTF8;
				mailMessage.BodyEncoding = Encoding.UTF8;
				mailMessage.Priority = priority;
				mailMessage.IsBodyHtml = isHtml;
				smtpClient.Send(mailMessage);
				SoftMailSendFailedCount = 0L;
				return true;
			}
			catch (Exception ex)
			{
				SoftMailSendFailedCount++;
				return false;
			}
		}
	}
}

其中smtp服务器和端口号需要注意

不知道的打开foxmail，一个邮件处理软件，官网即可下载https://www.foxmail.com/

 进去之后登录你要发送邮件的邮箱，找到设置

 同样的找到账户，然后选中你登录的账号，选择服务器，找到发件服务器和对应的端口号填进静态类中构造方法的参数去，值得一提的是默认ssl是打开的你需要关闭之后才能使用。修改之后点击应用即可

 最后调用方法：可以传参也可以不传。方法有很多种，具体的可以读一下静态类中的内容。随后调用即可，如果有写错或不对的地方还望纠正

public IActionResult email(string addr_to, string subject,string body)
        {//分别是收件地址，标题(20)，内容(2000)
            var result = SoftMail.MailSystem163.SendMail("收件的邮件账号", "标题", "内容。");
            return View();
        }

具体的运行demo更新：https://download.csdn.net/download/qq_53217825/87599054

点进去即可下载，设置的免费，csdn的尿性