With EWS got an exception explicit tls/ssl not supported, use implicit

We are using IMAP for inbound emails, now adding support for EWS and POP3 with the help of Rebex library.

var client = new Ews();
client.Settings.SslAcceptAllCertificates = true;
client.Settings.SslAllowedVersions = TlsVersion.TLS10 | TlsVersion.TLS11 | TlsVersion.TLS12;
client.ValidatingCertificate += new EventHandler<SslCertificateValidationEventArgs>(ValidateCertificate);

client.Connect(myServer, 443, SslMode.Explicit);
client.Login(myUser, myPwd);

which thrown an exception as, Explicit TLS/SSL not supported, use implicit TLS/SSL instead

I am using version 1.0.6026.0 of EWS library.

am i doing wrong in my test application or shouldn't use explicit instead use implicit?