SMTP Mail with ASP.net Error 5.5.1 Authentication Required

问题

Good day, I'm a beginner from using ASP.net and SMTP Mailer

Heres my Question, I always encounter this Error when i send email from my local and searched and tried the solutions around the net but not so lucky, I hope someone point out what codes do i need and where i encounter this errror

Message = "The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at"

Heres my Code:

protected void btnSendEmail_Click(object sender, EventArgs e)
        {
            // System.Web.Mail.SmtpMail.SmtpServer is obsolete in 2.0
            // System.Net.Mail.SmtpClient is the alternate class for this in 2.0
            SmtpClient smtpClient = new SmtpClient();
            MailMessage message = new MailMessage();

            try
            {
                MailAddress fromAddress = new MailAddress(txtEmail.Value, txtName.Value);
                smtpClient.Credentials = new System.Net.NetworkCredential("myUser@gmail", "password");
                // You can specify the host name or ipaddress of your server
                // Default in IIS will be localhost 
                smtpClient.Host = "smtp.gmail.com";
                smtpClient.EnableSsl = true;
                //Default port will be 25
                smtpClient.Port = 25;
                smtpClient.UseDefaultCredentials = false;
                //From address will be given as a MailAddress Object
                message.From = fromAddress;

                // To address collection of MailAddress
                message.To.Add("myEmail@gmail.com");
                message.Subject = txtSubject.Value;

                // CC and BCC optional
                // MailAddressCollection class is used to send the email to various users
                // You can specify Address as new MailAddress("admin1@yoursite.com")
                message.CC.Add("myEmail@gmail.com");

                // You can specify Address directly as string
                message.Bcc.Add(new MailAddress("myEmail@gmail.com"));

                //Body can be Html or text format
                //Specify true if it  is html message
                message.IsBodyHtml = false;

                // Message body content
                message.Body = txtaMessage.Value;
                message.BodyEncoding = System.Text.Encoding.UTF8;
                message.HeadersEncoding = System.Text.Encoding.UTF8;
                // Send SMTP mail
                smtpClient.Send(message);

                lblSuccess.Text = "Email successfully sent.";
            }
            catch (Exception ex)
            {
                lblSuccess.Text = "Send Email Failed.";
            }
        }

回答1:

Try this reference ASP Simple SMTP for C# and VB it helps me a lot for may smtp problem

回答2:

i tried to make a simple codes for sending email try this

MailMessage mm = new MailMessage(); mm.From = new MailAddress("fromEmail"); mm.To.Add("toEmail"); mm.CC.Add("ccEmail"); mm.Subject = "StringSubject"; mm.Body = "BodySubject"; mm.IsBodyHtml = true; SmtpClient smtp = new SmtpClient(); smtp.Host = "smtp.gmail.com"; smtp.EnableSsl = true; System.Net.NetworkCredential NetworkCred = new System.Net.NetworkCredential(); NetworkCred.UserName = "UsernameString"; NetworkCred.Password = "PasswordString"; smtp.UseDefaultCredentials = true; smtp.Credentials = NetworkCred; smtp.Port = 587; try { smtp.Send(mm); } catch (Exception) { }

回答3:

Please have a look on google support team, what they are saying regarding sending mail from application. https://support.google.com/mail/answer/78775?hl=en

Also following link can help you.

Gmail Error :The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required

回答4:

Goto Account of Gmail , then select Connected apps & sites Allow less secure apps: ON(if this is off you cannot send mails through apps,or your websites )

来源：https://stackoverflow.com/questions/31978816/smtp-mail-with-asp-net-error-5-5-1-authentication-required