Help with e-mail notifier connecting to Office365

Question

At my work, we have a custom built program that does some maintaining on databases and sharepoint. It also has an e-mail notifier to send out an e-mail if something messes up or if we have a shortage on a item in stock, etc. Yesterday the e-mailer stopped
working, and I think it has something to do with the EWS settings. When I try to run the code, it keeps giving a 403 Forbidden Error, like it can't connect to the server at all. The code is:
namespace DebugLogNotify
    public class notify
        public void SendEmail(List<string> tolist, string subject, string body, string fileattachment = null)
            ServicePointManager.ServerCertificateValidationCallback = CertificateValidationCallBack;
            ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2013);
            service.Credentials = new NetworkCredential("bizintel@*****.com", "*****", "*****.com");
            service.TraceEnabled = true;
            service.TraceFlags = TraceFlags.All;
            service.Url = new Uri("https://outlook.office365.com/EWS/Exchange.asmx");
            //service.AutodiscoverUrl("bizintel@*****.com", RedirectionUrlValidationCallback);
            EmailMessage email = new EmailMessage(service);
            email.From = new EmailAddress("WII Business Intel", "bizintel@*****.com");
            foreach (string s in tolist) { email.ToRecipients.Add(s); }
            email.ToRecipients.Add("ITAdmin@*****.com");
            email.Subject = subject;
            email.Body = new MessageBody(body);
            //email.Body.BodyType = BodyType.HTML;
            if (fileattachment != null) { email.Attachments.AddFileAttachment(fileattachment); }
            email.SendAndSaveCopy();
        private static bool CertificateValidationCallBack(    object sender,
                                            System.Security.Cryptography.X509Certificates.X509Certificate certificate,
                                            System.Security.Cryptography.X509Certificates.X509Chain chain,
                                            System.Net.Security.SslPolicyErrors sslPolicyErrors)
            // If the certificate is a valid, signed certificate, return true.
            if (sslPolicyErrors == System.Net.Security.SslPolicyErrors.None)
                return true;
            // If there are errors in the certificate chain, look at each error to determine the cause.
            if ((sslPolicyErrors & System.Net.Security.SslPolicyErrors.RemoteCertificateChainErrors) != 0)
                if (chain != null && chain.ChainStatus != null)
                    foreach (System.Security.Cryptography.X509Certificates.X509ChainStatus status in chain.ChainStatus)
                        if ((certificate.Subject == certificate.Issuer) &&
                           (status.Status == System.Security.Cryptography.X509Certificates.X509ChainStatusFlags.UntrustedRoot))
                            // Self-signed certificates with an untrusted root are valid. 
                            continue;
                        else
                            if (status.Status != System.Security.Cryptography.X509Certificates.X509ChainStatusFlags.NoError)
                                // If there are any other errors in the certificate chain, the certificate is invalid,
                                // so the method returns false.
                                return false;
                // When processing reaches this line, the only errors in the certificate chain are 
                // untrusted root errors for self-signed certificates. These certificates are valid
                // for default Exchange server installations, so return true.
                return true;
            else
                // In all other cases, return false.
                return false;
        private static bool RedirectionUrlValidationCallback(string redirectionUrl)
            // The default for the validation callback is to reject the URL.
            bool result = false;
            Uri redirectionUri = new Uri(redirectionUrl);
            // Validate the contents of the redirection URL. In this simple validation
            // callback, the redirection URL is considered valid if it is using HTTPS
            // to encrypt the authentication credentials. 
            if (redirectionUri.Scheme == "https")
                result = true;
            return result;
If you wouldn't mind letting me know what you think, I would really appreciate it!

Answer 1

This is a server side error from *****.com. You need to talk to the domain admin to see what is going on. No client side change can get around error unless you know if the server has a different code path somewhere. 
Visual C++ MVP