C# smtp.gmail.com:根据验证过程，远程证书无效：其他服务器工作正常

无法使用Google smtp.gmail.com邮件服务器发送电子邮件。同样的代码适用于outlook.office365.com邮件服务器。我搜索并尝试了在这个网站上找到的所有代码片段。下面是代码当前状态的快照

try
{
    string sSMTPServer = WebConfigurationManager.AppSettings["SMTPServer"];
    string sSMTPUsername = WebConfigurationManager.AppSettings["SMTPUsername"];
    string sSMTPPassword = WebConfigurationManager.AppSettings["SMTPPassword"];

    System.Net.Mail.SmtpClient emailClient = new System.Net.Mail.SmtpClient();
    emailClient.Host = sSMTPServer;
    emailClient.Credentials = new System.Net.NetworkCredential(sSMTPUsername, sSMTPPassword);
    emailClient.UseDefaultCredentials = true;
    emailClient.DeliveryMethod = SmtpDeliveryMethod.Network;

    emailClient.Port = 587; //produces "the remote certificate is invalid according to the validation procedure."
    //emailClient.Port = 465; produces "failure sending email" error

    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
    emailClient.EnableSsl = true;
    emailClient.Send(mailmessage);
    emailErrorHandler.errorThrown = false;
    emailErrorHandler.message = "Email Sent Successfully!";
}
catch (Exception ex)
{
    emailErrorHandler.errorThrown = true;
    emailErrorHandler.message = "error: " + ex.Message;
}

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希望这个问题对你有帮助！我们无法使用端口25，必须是安全端口587或465