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);