Session timeout error showing without sending mail

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C#

C#4.0

Hi,
Unable to send the mail using System.Net.mail using following code,always showing session timeout and I am unable to understand what the problem is.Please help

public bool SendEmail(string pTo, List<string> ccList, string pSubject, string pBody, string pAttachmentPath, string name)
        {
            string mailFrom = System.Web.Configuration.WebConfigurationManager.AppSettings["Email"];
            string mailPassword = System.Web.Configuration.WebConfigurationManager.AppSettings["Password"];
            string smptpServer = System.Web.Configuration.WebConfigurationManager.AppSettings["SmtpServer"];
            string smptpServerPort = System.Web.Configuration.WebConfigurationManager.AppSettings["SmtpServerPort"];
            NetworkCredential cred = new NetworkCredential(mailFrom, mailPassword, smptpServer);
            MailMessage myMail = new MailMessage();
            myMail.From = new MailAddress(mailFrom, "hai");
            myMail.To.Add(new MailAddress(pTo, name));
            myMail.IsBodyHtml = true;
            myMail.Subject = pSubject;
            myMail.Body = pBody;
            myMail.BodyEncoding = System.Text.Encoding.UTF8;
            myMail.Priority = MailPriority.High;
            if (ccList != null)
            {
                if (ccList.Count > 0)
                {
                    string ccEmailIdList = "";
                    foreach (string ccEmailId in ccList)
                    {
                        if (ccEmailIdList != "")
                        {
                            ccEmailIdList += ";";
                        }
                        ccEmailIdList += ccEmailId;
                    }
                    myMail.CC.Add(ccEmailIdList);
                }
            }
            if (pAttachmentPath.Trim() != "")
            {
                myMail.Attachments.Add(new Attachment(pAttachmentPath));
            }
            SmtpClient client = new SmtpClient(smptpServer, int.Parse(smptpServerPort));
            client.Credentials = cred;
            client.UseDefaultCredentials = false;
            client.DeliveryMethod = SmtpDeliveryMethod.Network;
            client.EnableSsl = true;
            client.Send(myMail);
            return true;
        }