How to send Email through Window Services in C#

Exception Details: System.Net.Mail.SmtpException: The operation has timed out.

public  bool SendEmail()
        {            
            List<dbomjobqueue> pendingJobQuoueList = getPendingJobQuoue();
            
                foreach (var list in pendingJobQuoueList)
                {
                    if (list.fromStatus == 0)
                    {
                        ID = list.ID;
                        toEmail = list.toEmail;
                        fromPath = list.fromPath;
                        fromStatus = list.fromStatus;
                        subject = "";
                        //Creating an instance of the mail object
                        MailMessage mailMsg = new MailMessage();
                        MailAddress mailAddress = null;
                        try
                        {
                            //Set the content
                            mailMsg.IsBodyHtml = true;  // Set the format of the mail message body as HTML
                            mailMsg.To.Add(toEmail);    // Set the recepient address of the mail message                     
                            mailAddress = new MailAddress("muna.angul10@gmail.com");
                            mailMsg.From = mailAddress; // Set the sender address of the mail message
                            mailMsg.Subject = subject;  // Set the subject of the mail message
                            mailMsg.Body = "";  // Set the body of the mail message
                            mailMsg.Priority = MailPriority.High;   // Set the priority of the mail message to high
                            mailMsg.Attachments.Add(new Attachment(fromPath));  //create and add the attachment
                            SmtpClient smtpClient = new SmtpClient();   //smtp server address
                            System.Net.NetworkCredential credentials = new System.Net.NetworkCredential();
                            smtpClient.Credentials = credentials;
                            //smtpClient.Host = "localhost"or"192.168.30.137";
                            smtpClient.EnableSsl = true;
                            //smtpClient.UseDefaultCredentials = false;
                            smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
                            if (ID != 0)
                            {
                                fromStatus = 1; //Sending In Progress 
                                UpdateDbStatus();
                            }
                            smtpClient.Send(mailMsg);                            
                            eventLogDBOMJobQueue.WriteEntry("Mail Send Successfully");
                            //fromStatus = 2;//Email send successfully(Done)
                            //UpdateDbStatus();
                        }
                        catch (Exception ex)
                        {                           
                            errorDescription = ex.Message;
                            //fromStatus = 3;//Error
                            //UpdateDbStatus();
                            return false;
                        }
                        finally
                        {
                            mailMsg = null;
                            mailAddress = null;
                        }
                 }
            }
            return true; 
}

<system.net>
    <mailSettings>
      <smtp>
        <network host="smtpcorp.com" port="465" userName="username" password="password" defaultCredentials="true" />
        <!--<network host="smtp.gmail.com" port="465" />-->
      </smtp>
    </mailSettings>
  </system.net>