JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" data-bind="value: modelName" />
    
    
    <div data-bind="foreach: addresses">
      <input type="text" data-bind="value: $rawData.address, valueUpdate: 'input'" />
      <button data-bind="click: $parent.removeAddress">Remove</button>
      <br/>
    </div>
    
    <button data-bind="visible: allowAddMore, click: addNew">Add</button>
    
       <pre data-bind="text: ko.toJSON($data, null, 2)"></pre>

JavaScript

var Model = function() {
  
  var self = this;
  self.modelName = ko.observable("modelName");
  self.maxCount = 4;
  self.addresses = ko.observableArray();
  
  self.addUser = function(email) {
    self.addresses.push({address: email});
  };
  
  self.removeAddress = function(email) {
    self.addresses.remove(email);
  }
  
  self.hasEmpty = ko.computed(function() {
    var hasBlank = false;
    
    ko.utils.arrayForEach(self.addresses(), function(item){     
      if (item.address === ""){
        hasBlank = true;
        return;
      }
    });
    
    return hasBlank;
  });
  
  self.allowAddMore = ko.computed(function() {
    return self.hasEmpty() === false && self.addresses.length <= self.maxCount;
  });
  
  self.addNew = function() {
    if (!self.hasEmpty()){
      self.addresses.push({address: ''});
    }
  };

  
};



  var vm = new Model();
  vm.addUser("foo@bar.com");
  vm.addUser("foo1@bar1.com");
  vm.addUser("foo2@bar2.com");
  vm.addUser("foo3@bar3.com");
  ko.applyBindings(vm);