Could not connect to mail server.

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SQL-Server-2008R2

I am using gmail id to send mail from database. It is working fine till yesterday, But when I start using same Id to send mail from C# code. The Database Alert mail is not working.
Error Message is:
Mail queued.

The mail could not be sent to the recipients because of the mail server failure. (Sending Mail using Account 1 (2014-06-05T08:30:00). Exception Message: Could not connect to mail server. (Attempted to read or write protected memory. This is often an indication that other memory is corrupt.).

Database Mail code is as below:

EXEC msdb.dbo.sp_send_dbmail
@profile_name ='Mail Profile Name', 
@body = 'test message',
@body_format ='HTML',
@recipients ='myid@gmail.com', 
@subject = 'TEST MAIL FROM DB' ;

The C# Code is as below:

MailMessage mail = new MailMessage();
SmtpClient smtpC = new SmtpClient("smtp.gmail.com");  
mail.From = new MailAddress(fromMailId);
mail.To.Add(toMailId);
mail.Subject = "Subject";
mail.Body = "Message in html format";
mail.IsBodyHtml = true;
smtpC.Port = 587;
smtpC.Credentials = new System.Net.NetworkCredential(fromMailId, password);
smtpC.EnableSsl = true; 
smtpC.Send(mail);

Please help me to solve this, I am facing problem on live server.