连接到主机端口25时出现问题

我在Arvixe工作了很多年，最近他们更改了所有权并执行了各种迁移。他们的许多客户都遇到了问题。

这是ASP.NET 4.5 Web应用程序

自从他们迁移以来，当我的网站用户试图通过以下表格发送电子邮件时，我会遇到异常：http://goo.gl/zz7FeH

消息"无法连接到远程服务器"

InnerException｛"连接尝试失败是因为连接方在一段时间后没有正确响应，或者建立的连接失败是因为所连接的主机未能响应104.27.1.886.185:25"｝System.Exception｛System.Net.SocketException｝

我已经用Telnet检查了这个端口，似乎可以连接：telnet smtp.davincispainting.com 25

这是邮件服务代码：

public class EstimateContactInfo
{
public string Email { get; set; }
public string Name { get; set; }
public string Company { get; set; }
public string Address1 { get; set; }
public string Address2 { get; set; }
public string Phone { get; set; }
public string City { get; set; }
public string State { get; set; }
//public string Zip { get; set; }
public string Customer { get; set; }
public string ServiceType { get; set; }
public string JobDescription { get; set; }
public override string ToString()
{
    return string.Format(@"Name: {0}<br/><br/>Company: {1}<br/><br/>Email Address: {2}<br/><br/>Phone: {3}<br/><br/>
            Address1: {4}<br/><br/>Address2: {5}<br/><br/>City: {6}<br/><br/>Sate: {7}<br/><br/>Customer: {8}<br/><br/>ServiceType: {9}<br/><br/>JobDescription: {10}",
            Name, Company, Email, Phone, Address1, Address2, City, State, Customer, ServiceType, JobDescription);
}
}
public class MailService
{
public MailService()
{
}
private bool IsValidateEmail(string email)
{
    return Regex.IsMatch(email, @".*@.{2,}'..{2,}");
}
public string GetToken(int contactNum)
{
    string extendKey = string.Format("smcf-{0}{1}{2}", System.Configuration.ConfigurationManager.AppSettings["ContactEmail" + contactNum.ToString()], DateTime.Now.Month, DateTime.Now.Day);
    Byte[] originalBytes;
    Byte[] encodedBytes;
    MD5 md5;
    //Instantiate MD5CryptoServiceProvider, get bytes for original password and compute hash (encoded password)
    md5 = new MD5CryptoServiceProvider();
    originalBytes = ASCIIEncoding.Default.GetBytes(extendKey);
    encodedBytes = md5.ComputeHash(originalBytes);
    //Convert encoded bytes back to a 'readable' string
    return BitConverter.ToString(encodedBytes);
}
public void SendMail(string from, string to, string subject, string content, string cc)
{
    if (!IsValidateEmail(from))
    {
        from = to;
        subject += " - invalid email";
        content += "'n'nBad email:" + content;
        cc = null;
    }
    MailMessage message = new MailMessage(from, to, subject, content);
    message.IsBodyHtml = true;
    if (cc != null)
        message.CC.Add(cc);
    SmtpClient emailClient = new SmtpClient("mail.davincispainting.com", 25);
    string pwd = "ninja71";
    NetworkCredential credentials = new NetworkCredential(from, pwd);
    emailClient.Credentials = credentials;
    emailClient.Send(message);
}
public void SubmitContact(EstimateContactInfo contactInfo, int cc)
{
    //SendMail(System.Configuration.ConfigurationManager.AppSettings["ContactEmail1"], System.Configuration.ConfigurationManager.AppSettings["ContactEmail1"], "Request Estimate", contactInfo.ToString(), cc > 0 ? contactInfo.Email : null);
    SendMail(ConfigurationManager.AppSettings["ContactEmail1"], System.Configuration.ConfigurationManager.AppSettings["ContactEmail1"], "Request Estimate", contactInfo.ToString(), cc > 0 ? contactInfo.Email : null);
}
}

这是对MailService.cs:的呼叫

public partial class painting_estimate : System.Web.UI.Page
{
    protected void btnSendGenMail_Click(object sender, EventArgs e)
    {
        try
        {
            MailService mailService = new MailService();
            EstimateContactInfo contactInfo = new EstimateContactInfo();
            contactInfo.Name = txtGenName.Text;
            contactInfo.Company = txtGenCompany.Text;
            contactInfo.Email = txtGenEmail.Text;
            contactInfo.Phone = txtGenPhone.Text;
            contactInfo.Address1 = txtGenAddy1.Text;
            contactInfo.Address2 = txtGenAddy2.Text;
            contactInfo.City = txtGenCity.Text;
            contactInfo.State = ddGenState.Text;
            contactInfo.Customer = ddGenCustomer.SelectedItem.Text;
            contactInfo.ServiceType = ddGenJobType.SelectedItem.Text;
            contactInfo.JobDescription = txtGenMessage.Text;
            mailService.SubmitContact(contactInfo, 0);
            SubmitSuccess.Visible = true;
        }
        catch (Exception se)
        {
            SubmitError.Visible = true;
        }
        ContactPanel.Visible = false;
    }