执行telnet测试以查看如果您可以连接到Gmail SMTP服务器。您可以在此处找到以下步骤：https： //   support.google.com/mail/answer/78775?hl=en  

I have been struggling with this problem for days now i dont know what to do because everyone is saying the code I am using to send an email should work i have even tried different ports from 587 to 25 to 465 I just do not know anymore i have even added an SmtpFailedRecipientsException and still the same problem could someone please help me i need to launch this project im behind schedule.

string UserName="xhasiwe@gmail.com";
string Password="mypassword";

MailMessage mail = new MailMessage();
SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com");
String report = null;
mail.From = new MailAddress("xhasiwe@gmail.com");
string connString = @"Provider=Microsoft.ACE.OLEDB.12.0;"
                    + @"Data Source= C:\Temp\F1\Docs\Expeditors Project\TestDatabase.accdb";

// Create an OleDbConnection from the provided connection string.
using (OleDbConnection connection = new OleDbConnection(connString))
{
    //List to store information
    List<String> EmployeeEMailAddress = new List<String>();

    // Open a connection to database.
    connection.Open();
    OleDbDataReader reader = null;

    // Set up a command with the given query and associate this with the current connection.
    OleDbCommand command = new OleDbCommand("SELECT [EmployeeEMailAddress], [TimeOut] FROM Table1 WHERE [TimeOut] is null", connection);
    // Read data returned for the query
    reader = command.ExecuteReader();
    while (reader.Read())
    {
        EmployeeEMailAddress.Add(reader["EmployeeEMailAddress"].ToString());
    }

    foreach (string value in EmployeeEMailAddress ) 
    {
        //If you want to know how many times the elements are repeated
        //This will return a List of an anonymous type, and each element will have the properties Element and Counter, to retrieve the informations you need.
        if (value != "\"\"")
        {
            var result = EmployeeEMailAddress.GroupBy(item => item)
                                             .Select(item => new
                                             {
                                                 Name = item.Key,
                                                 Count = item.Count()
                                             })
                                             .OrderByDescending(item => item.Count)
                                             .ThenBy(item => item.Name);
            report = String.Join(Environment.NewLine, result
            .Select(item => String.Format("{0} , {1} ;", item.Name, item.Count)));

        }        
    }
    connection.Close();   
    String [] rfqCount = report.Split(';');
    int ct = 0;
    for (int i = 0; i < rfqCount.Length; i++)
    {
        if (rfqCount[i].Trim() != "")
        {
            ct++;
        }
    }
    
    String[] emd = rfqCount[ct-1].Trim().Split(',');
    
    String emailadd = emd[0];
    mail.To.Add(emailadd);
}

mail.Subject = ReadEmailevent.TypeOfRequest;
mail.Body = ReadEmailevent.Body;

SmtpServer.Port = 25;
SmtpServer.Credentials = new System.Net.NetworkCredential(UserName, Password);
SmtpServer.EnableSsl = true;

try
{
    SmtpServer.Send(mail);
}
catch (SmtpFailedRecipientsException ex)
{
    for (int i = 0; i < ex.InnerExceptions.Length; i++)
    {
        SmtpStatusCode status = ex.InnerExceptions[i].StatusCode;
        if (status == SmtpStatusCode.MailboxBusy ||
            status == SmtpStatusCode.MailboxUnavailable)
        {
            Console.WriteLine("Delivery failed - retrying in 5 seconds.");
            System.Threading.Thread.Sleep(5000);
            SmtpServer.Send(mail);
        }
        else
        {
            Console.WriteLine("Failed to deliver message to {0}",
                ex.InnerExceptions[i].FailedRecipient);
        }
    }
}

perform a telnet test to see if you can connect to Gmail SMTP server. You can find steps here: https://support.google.com/mail/answer/78775?hl=en