在活动服务器上出现SMTP类错误

我有一个网站与ASP。.NET MVC后端运行。NET 3.5。在这个网站上，有一个脚本使用gmail作为邮件服务发送电子邮件。该脚本在我的开发机器上运行并在本地发送邮件，但是一旦我将其上传到活动服务器，它就会失败。目前它给我的唯一错误信息是(因为我告诉过它，你将在下面看到):

The transport failed to connect to the server.

以下是邮件发送脚本的代码:

using System.Net.Mail;
using System.Web.Mail;
using MailMessage = System.Web.Mail.MailMessage;
namespace MySite.Helpers
{
    public class GmailHelper
    {
        private readonly int _port = 465;
        private readonly string _accountName;
        private readonly string _password;
        public GmailHelper(string accountName, string password)
        {
            _accountName = accountName;
            _password = password;
        }
        public GmailHelper(string accountName, string password, int port)
        {
            _accountName = accountName;
            _password = password;
            _port = port;
        }
        public void Send(string from, string to, string subject, string body, bool isHtml)
        {
            Send(from, to, subject, body, isHtml, null);
        }
        public void Send(string from, string to, string subject, string body, bool isHtml, string[] attachments)
        {
            var mailMessage = new MailMessage
                                                          {
                                                              From = from,
                                                              To = to,
                                                              Subject = subject,
                                                              Body = body,
                                                              BodyFormat = isHtml ? MailFormat.Html : MailFormat.Text
                                                          };

            // Add attachments
            if (attachments != null)
            {
                foreach (var t in attachments)
                {
                    mailMessage.Attachments.Add(new Attachment(t));
                }
            }
            //  Authenticate
            mailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", 1);
            // Username for gmail - email@domain.com for email for Google Apps
            mailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", _accountName);
            // Password for gmail account
            mailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", _password);
            // Google says to use 465 or 587.  I don't get an answer on 587 and 465 works - YMMV
            mailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpserverport", _port.ToString());
            // STARTTLS 
            mailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpusessl", true);
            // assign outgoing gmail server
            SmtpMail.SmtpServer = "smtp.gmail.com";
            SmtpMail.Send(mailMessage);
        }
    }
}

它的名字是这样的:

[HttpPost]
public ActionResult Employment(EmploymentModel model, FormCollection collection)
{
    if (!ModelState.IsValid)
        return View(model);
    var results = new EmploymentViewModel();
    try
    {
        results.Position = model.Position;
        results.FirstName = model.FirstName;
        results.LastName = model.LastName;
        results.ContactPhone = model.ContactPhone;
        results.OtherPhone = model.OtherPhone;
        results.Address = model.Address;
        results.Email = model.Email;
        results.HsDiploma = model.HsDiploma.ToString();
        results.CollegeYears = model.CollegeYears;
        results.Skills = model.Skills;
        results.Employment = model.Employment;
        results.DateSent = DateTime.Now.ToString("MM/dd/yyyy HH:mm:ss");
        var gmail = new GmailHelper("noreply@mysite.com", "[*removed*]");
        var fromAddress = new MailAddress("noreply@mysite.com", "MySite");
        var toAddress = new MailAddress("applications@mysite.com", "MySite Employment");
        var subject = string.Format("Employment Application for {0} {1}", model.FirstName, model.LastName);
        gmail.Send(fromAddress.Address, toAddress.Address, subject, EmployMailBody(results), false);
    }
    catch (Exception ex)
    {
        results.Sent = false;
        results.Title = "Oops, our mail drone seems to have malfunctioned!";
        results.Message = string.Format("We appologize, {0} {1}, but our email system has encountered an error and your email was not sent.</p>",
                results.FirstName, results.LastName);
        results.Message += Environment.NewLine + "<p>Please try your request later, or fax your résumé to our Corporate office.";
        results.Message += Environment.NewLine + JQueryHelpers.GenerateErrorField(ex.Message);
        return View("EmploymentSubmit", results);
    }
    results.Sent = true;
    results.Title = "Thank you for your submission!";
    results.Message = string.Format("Thank you for your interest in joining our team, {0} {1}!</p>", results.FirstName, results.LastName);
    results.Message += Environment.NewLine + "<p>We have successfully recieved your information and will contact you shortly at the number your have provided.";
    return View("EmploymentSubmit", results);
}

我99%肯定它在网站上出现之前是正常的，但我可能错了，因为我已经更新了一个月左右的网站。

是否有一些额外的步骤，我可以采取调试这个"更好"跟踪潜在的问题，或者我搞砸了我的代码在某个地方不小心?

谢谢!

<标题> EDIT1 h1> 以我更新类严格使用System.Net.Mail。我成功地从我的开发机器发送了一条消息。然而，当我将站点上传到服务器时，我得到了一个新的错误消息:

Request for the permission of type 'System.Net.Mail.SmtpPermission, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.

这个网站是通过godaddy.com托管的，在搜索了一下之后，似乎godaddy只允许通过他们的smtp服务器中继。看起来我必须更改主机提供商才能使其正常工作。

谢谢!

<标题> EDIT2 h1> 从godaddy转移到gmail的原因是最初当我有这个脚本时，电子邮件将需要15到45分钟才能到达目的地。这可能是我之前使用的弃用代码，但无论如何，它现在都在几秒钟内被分派和到达，就像它应该的那样。这是我的GoDaddy帮助类，以防它会帮助别人:

public class GoDaddyHelperNet
{
    private readonly int _port = 25;
    private readonly MailAddress _accountName;
    private readonly string _password;
    private readonly string _host = "relay-hosting.secureserver.net";
    public GoDaddyHelperNet(MailAddress accountName, string password)
    {
        _accountName = accountName;
        _password = password;
    }
    public GoDaddyHelperNet(MailAddress accountName, string password, int port)
    {
        _accountName = accountName;
        _password = password;
        _port = port;
    }
    public GoDaddyHelperNet(MailAddress accountName, string password, int port, string host)
    {
        _accountName = accountName;
        _password = password;
        _port = port;
        _host = host;
    }
    public void Send(MailAddress to, string subject, string body, bool isHtml)
    {
        Send(_accountName, to, subject, body, isHtml);
    }
    public void Send(MailAddress from, MailAddress to, string subject, string body, bool isHtml)
    {
        var smtp = new SmtpClient
                       {
                           Host = _host,
                           Port = _port,
                           EnableSsl = false,
                           DeliveryMethod = SmtpDeliveryMethod.Network,
                           UseDefaultCredentials = false,
                           Credentials = new NetworkCredential(from.Address, _password),
                           Timeout = 15000
                       };
        using (var message = new System.Net.Mail.MailMessage(from.Address, to.Address)
                     {
                         Subject = subject,
                         Body = body,
                     })
            smtp.Send(message);
    }
}