SMTP 服务器要求安全连接或客户端未通过身份验证。 服务器响应为: 5.5.1 Authentication Required. Learn more at

Question

                            MailAddress emailfrom = new System.Net.Mail.MailAddress("**********@sina.cn");
                            MailAddress emailto = new System.Net.Mail.MailAddress("********@qq.com");
                            MailMessage email = new System.Net.Mail.MailMessage(emailfrom, emailto);
                            //email.Bcc.Add(new System.Net.Mail.MailAddress(textBox2.Text.ToString().Trim()));
                            //email.CC.Add(new System.Net.Mail.MailAddress(textBox2.Text.ToString().Trim()));
                            email.Subject = textBox3.Text;
                            email.Body = richTextBox1.Text.ToString().Trim();
                            email.SubjectEncoding = System.Text.Encoding.UTF8;
                            email.IsBodyHtml = true;
                            email.Priority = System.Net.Mail.MailPriority.Normal;
                            SmtpClient smtpPC = new SmtpClient("smtp.sina.com.cn",25);
                            smtpPC.DeliveryMethod = SmtpDeliveryMethod.Network;
                            smtpPC.Credentials = new System.Net.NetworkCredentia("用户名", "密码");
                            smtpPC.UseDefaultCredentials = false;
                            smtpPC.EnableSsl = true;
                            //MailMessage my = new MailMessage();
                            try
                            {
                                smtpPC.Send(email);
                                MessageBox.Show("ok,send email complete!");
                            }
                            catch (Exception ex)
                            {
                                MessageBox.Show(ex.Message);
                            }

Answer 1

我也遇到这个问题了，不过我已经解决了
smtpHost=Smtp.gmail.com
SmtpClient client = new SmtpClient(smtpHost,587);
client.EnableSsl = true;
因为Gmail要求把ssl加密打开