Error - 'The SMTP server requires a secure connection or the client was not authenticated

Question

User1979860870 posted

protected void sendEmail(string address, string subject, string from, string body)
        {
            System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage();
            message.To.Add(address);
            message.Subject = subject;
            message.From = new System.Net.Mail.MailAddress(from);
            message.Body = body;
            System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("smtp.gmail.com");
            smtp.Credentials = new System.Net.NetworkCredential("[e-mail]", "xxxx");

            smtp.Port = 587;
            smtp.EnableSsl = true;
            smtp.Send(message);

        }

Hi

<div>protected void sendEmail(string address, string subject, string from, string body)</div> <div>        {</div> <div>            System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage();</div> <div>            message.To.Add(address);</div> <div>            message.Subject = subject;</div> <div>            message.From = new System.Net.Mail.MailAddress(from);</div> <div>            message.Body = body;</div> <div>            System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("smtp.gmail.com");</div> <div>            smtp.Credentials = new System.Net.NetworkCredential("[e-mail]", "XXXXX");</div> <div>            smtp.Port = 587;</div> <div>            smtp.EnableSsl = true;</div> <div>            smtp.Send(message);</div> <div> </div> <div>        }</div>

Thanks

Answer 1

User-939850651 posted

Hi jagjit saini,

I'm not sure if you have modified the setting in Less secure app access setting to "turn on", so that you can use gmail to send mail in third-party applications.

According to the code you provided, you also need to set UseDefaultCredentials property to "false", something like this:

protected void sendEmail(string address, string subject, string from, string body)
        {
            System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage();
            message.To.Add(address);
            message.Subject = subject;
            message.From = new System.Net.Mail.MailAddress(from);
            message.Body = body;
            System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("smtp.gmail.com");
            smtp.Credentials = new System.Net.NetworkCredential("[e-mail]", "xxxx");

            smtp.Port = 587;
            smtp.EnableSsl = true;
            smtp.UseDefaultCredentials = false;
            smtp.Send(message);

        }

Hope this can help you.

Best regards,

Xudong Peng