EWS : Mail added to Sent Items but not delivered

Question

I am using Microsoft Exchange Web Services - EWS Managed API 2.2 to send mails from my Exchange Server email. Here's the code I am using :

ServicePointManager.ServerCertificateValidationCallback = CertificateValidationCallBack;
ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP1);
service.Credentials = new WebCredentials("UserName", "Password", "domain");
service.Url = new Uri("https://exchangeserver.com/EWS/Exchange.asmx");
EmailMessage email = new EmailMessage(service);
//email.ToRecipients.Add("example@hotmail.com");
email.ToRecipients.Add("example@gmail.com");
email.ToRecipients.Add("username@domain.com");
email.Body = new MessageBody("BODY!");

email.SendAndSaveCopy();


//Here is my Certificate Validation function taken straight from MSDN :

static private 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;
    }
}

If I set the ToEmailAddress as the login username itself, the mail is being sent to inbox. If I send to any other email address(tried gmail,hotmail,yahoo), the mail is deposited in the sent mail, but it is not delivered to the email address intended. But if I login to Outlook Web App and type a mail and send, the mail is added to Sent Items as well as delivered to the recipent email address.

I have checked Spam/Junk folder etc. The credentials are correct because I am able to save the copy of mail in Sent Items.

What is it that I am doing wrong?

Answer 1

It turns out the mail was being spammed out at the outgoing exchange server itself. If I set a meaningful Subject, the mail was being sent.

email.Subject = "Some meaningful subject";