the operation has timed out error exception when send mail

protected bool SendMail()
        {
            //MessageBox.Show(plainText);
            bool send = true;
            try
            {
                MailMessage mail = new MailMessage();
                SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com");
                mail.From = new MailAddress(fromMail);
                //mail.To.Add(email);


                var distinctAddress = new List<string>(email.Split(',').Distinct());
                //mail.To = string.Empty;

                foreach (string address in distinctAddress) // Loop through all strings
                {
                    mail.To.Add(address) ;//= address + ","; 
                    emailsList.Add(address);
                }
                //this.To = this.To.TrimEnd(',');
                //mail.To.Add(this.To);

                mail.Subject = subject;
                mail.Body = body;
                mail.IsBodyHtml = true;
                mail.BodyEncoding = System.Text.Encoding.UTF8;
                //if (!String.IsNullOrWhiteSpace(filePath))
                if(filesPathList.Count > 0)
                {
                    for (int i = 0; i < filesPathList.Count; i++)
                    {
                        mail.Attachments.Add(new Attachment(filesPathList[i]));
                    }
                }

                if (uploadsPathList.Count > 0)
                {
                    for (int i = 0; i < uploadsPathList.Count; i++)
                    {
                        mail.Attachments.Add(new Attachment(uploadsPathList[i]));
                    }
                }
                SmtpServer.Port = 587;
                SmtpServer.Credentials = new System.Net.NetworkCredential(fromMail, fromPass);
                SmtpServer.EnableSsl = true;
                SmtpServer.Send(mail);
                
            }
            catch (Exception ex)
            {
                send = false;
                MessageBox.Show(ex.ToString());
            }
            return send;
        }