C# Winform 发送邮件

using System.Net.Mail;

private void SendMail()
        {

            System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient("smtp.163.com");

            client.UseDefaultCredentials = true;//设置为发送认证消息               这句和下一句不要遗漏。
            client.Credentials = new System.Net.NetworkCredential("[e-mail]", "mymailpassword");//认证消息
            System.Net.Mail.MailMessage mess = new System.Net.Mail.MailMessage();
            mess.From = new System.Net.Mail.MailAddress("[e-mail]", "My Name");
            mess.To.Add(new System.Net.Mail.MailAddress("[e-mail]", "Your Name"));
            mess.Subject = "主题（测试）";
            mess.Body = "正文:" + "\r\n" + "每天自动邮件。内容还没想好。";
            try
            {
                client.Send(mess);
                MessageBox.Show("发送成功完成");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);

            }

}

注意：

如果是QQ邮箱的，还需要在邮箱那里设置SMTP。