onSuccessCallback.onSuccess() not being called when .withProcessVisibility(false)

I want remove ProgressDialog when sending email, so I add to builder  .withProcessVisibility(false). Now ProgressDialog dialog not showing but onSuccess() not being called.
```
 .withOnSuccessCallback(new BackgroundMail.OnSuccessCallback() {
     @Override
     public void onSuccess() {
            Log.i("MY_PROG", "message sended");
     }
})
```