AngularJS : ng-selectize is not initializing selctize options after AJAX call - ajax

Question

I'm using ng-selectize directive to a select box using angularJS. Options to the slectbox are retrieved from an AJAX call. AJAX call response is coming in proper format.If do inspect element, select box options are populated properly. But in the UI, options are not rendered. Is there any specific reason for this behaviour? The same code is working fine in another place.
Here is my code:
HTML:
<select multiple="multiple"
ng-model="email.existing"
ng-options="obj.email for obj in emailLists track by obj.email"
placeholder="Choose from existing email address"
selectize>
Javascript
angular.module('myApp', [
'myApp.controllers',
'myApp.services',
'ngDialog',
'angular-selectize'
]);
angular.module('myApp.services', []).
factory('myAPIservice', function($http) {
var myAPI = {};
myAPI.getAllEmail = function( data ) {
return $http.post(APP_BASE_URL + "director/getallemail", data );
}
return myAPI;
});
angular.module('myApp.controllers', [])
.controller('myCntrl', function($scope, myAPIservice, ngDialog) {
myAPIservice.getAllDirectorsEmail({}).success(function (response) {
$scope.emailLists = response;
});
});
The above code retrieves email list from url. Sample response will look like this.
AJAX Response
If I change the javascript code to
angular.module('myApp.controllers', [])
.controller('myCntrl', function($scope, myAPIservice, ngDialog) {
$scope.emailLists = new Array({email:'abc#def.com'},{email:'lmn#opqr.com'})
});
and the response will be
Without AJAX call
Can anyone help me resolve this issue?