office365 SMTP Error: Failure sending mail in C#

I m trying to send an email with below code it run correctly and email sent on live server but when i try to send an email using locally with the same code, the email is not getting sent.

It gives error "failure sending mail". 

smtp.office365.com

port=587

        public void SendMail(string recipient, string subject, string body, string AttachmentFiles = null, string cc = "", string bcc = "")
        {
            //SmtpClient client = new SmtpClient("smtp-mail.outlook.com");

            SmtpClient client = new SmtpClient(ConfigurationManager.AppSettings["SMTP_SERVER"].ToString());


            client.Port = Convert.ToInt32(ConfigurationManager.AppSettings["SMTP_PORT"].ToString());
            client.DeliveryMethod = SmtpDeliveryMethod.Network;
            client.UseDefaultCredentials = false;
            System.Net.NetworkCredential credentials = new System.Net.NetworkCredential(ConfigurationManager.AppSettings["NetworkCredential_UserId"].ToString(), ConfigurationManager.AppSettings["NetworkCredential_Password"].ToString());
            client.EnableSsl = true;
            client.Credentials = credentials;

            try
            {
                var mail = new MailMessage();
                string from = "";

                from = ConfigurationManager.AppSettings["NetworkCredential_UserId"].ToString();

                if (!string.IsNullOrEmpty(from.Trim()))
                {
                    mail.From = new MailAddress(from);
                }

                if (!string.IsNullOrEmpty(recipient.Trim()))
                {

                    foreach (var address in recipient.Split(new[] { ";" }, StringSplitOptions.RemoveEmptyEntries))
                    {
                        mail.To.Add(address);
                    }
                    //mail.To.Add(recipient);
                }

                if (!string.IsNullOrEmpty(cc.Trim()))
                {
                    foreach (var ccaddress in cc.Split(new[] { ";" }, StringSplitOptions.RemoveEmptyEntries))
                    {
                        mail.CC.Add(ccaddress);
                    }
                    //mail.CC.Add(cc);
                }

                if (!string.IsNullOrEmpty(bcc.Trim()))
                {
                    foreach (var bccaddress in bcc.Split(new[] { ";" }, StringSplitOptions.RemoveEmptyEntries))
                    {
                        mail.Bcc.Add(bccaddress);
                    }
                    //mail.Bcc.Add(bcc);
                }


                mail.Subject = subject;
                mail.IsBodyHtml = true;
                mail.Body = body;


                if (!string.IsNullOrEmpty(AttachmentFiles))
                {
                    foreach (string a in AttachmentFiles.Split(new char[] { ',' }))
                    {
                        if (!string.IsNullOrEmpty(a))
                        {
                            Attachment att = new Attachment(a);
                            mail.Attachments.Add(att);
                        }
                    }
                }

                client.Send(mail);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                throw ex;
            }
        }