SMTP 服务器需要安全连接或客户端未通过身份验证

Question

我收到了这个错误

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>

代码文件

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);
        }

Answer 1

这对我有用：

1. 需要在 Google 帐户（来自电子邮件）上打开“访问安全性较低的应用程序”。
2. 设置 smtpclient.UseDefaultCredentials = false;

3. 设置 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);
   

Answer 2

实际上，您可以在 web.config 文件中通过添加 enableSsl="true" 来处理这个问题。这对我有用，我不需要在代码中做任何事情。

例如

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

Answer 3

尝试将EnableSsl 属性设置为true：

smtpClient.EnableSsl = true;

AFAIK 这个属性只能在代码中设置，不能在配置文件中指定。