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

Question

I am getting this error

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first. e17sm974159fak.34

Web.config

<mailSettings>
    <smtp deliveryMethod="Network"
                from="emailaccount@gmail.com">
        <network defaultCredentials="false" host="smtp.gmail.com" port="587"
                    userName="emailaccount@gmail.com"  password="12345678" />
    </smtp>        
</mailSettings>

Code file

public void Submit()
        {
            EnsureCurrentlyValid();
            // Send via email
            var message = new StringBuilder();
            message.AppendFormat("Date: {0:yyyy-MM-dd hh:mm}\n", DateTime.Now);
            message.AppendFormat("Email from: {0}\n", Name);
            message.AppendFormat("Email: {0}\n", Email);
            message.AppendFormat("Message: {0}\n", Message);
            SmtpClient smtpClient = new SmtpClient();
            MailMessage m = new MailMessage(
                "visitor@mydomain.com", // From
                "emailaccount@gmail.com", // To
                "Suggestion/Comments", // Subject
                message.ToString()); // Body

            smtpClient.Send(m);
        }

Hello @coure2011 , If you get the solution of your problem then please help me, because I am getting the same error. — Abhishek, Jul 23 '16 at 06:35

score 51 · Accepted Answer · answered Dec 20 '10 at 18:14

51

Try setting the EnableSsl property to true:

smtpClient.EnableSsl = true;

AFAIK this property can only be set in code and cannot be specified in the config file.

answered Dec 20 '10 at 18:14

Darin Dimitrov

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See also: http://stackoverflow.com/questions/32260/sending-email-in-net-through-gmail – Paul Wheeler Dec 20 '10 at 18:17

score 21 · Answer 2 · edited Jan 18 '12 at 15:42

21

Actually you can handle this in your web.config file by adding enableSsl="true". This worked for me and I didn't need to do anything in code.

e.g.

<network host="smtp.gmail.com" enableSsl="true" ... />

edited Jan 18 '12 at 15:42

quentin-starin

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answered Dec 20 '11 at 04:03

Michael

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6

enableSSl is only supported in .net 4+ – AndyM Mar 26 '12 at 10:07

score 0 · Answer 3 · answered Jan 11 '19 at 16:54

This worked for me:

Need to turn on "Access for less secure apps" on google account(From Email).
Set smtpclient.UseDefaultCredentials = false;

Set smtpclient.EnableSsl = true;

    MailMessage mail = new MailMessage("FromEmail_Address", "ToEmail_Address");
    SmtpClient smtpclient = new SmtpClient();
    smtpclient.Port = 587;
    smtpclient.DeliveryMethod = SmtpDeliveryMethod.Network;
    smtpclient.UseDefaultCredentials = false;
    smtpclient.Host = "smtp.gmail.com";
    smtpclient.UseDefaultCredentials = false;
    mail.Subject = "Email Subject";
    mail.Body = "Content of the email";
    smtpclient.EnableSsl = true;
    smtpclient.Credentials = new System.Net.NetworkCredential()
    {
        UserName = "FromEmail_Address",
        Password = "password of the email"
    };
    client.Send(mail);

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

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