Callback or promise never is completed through EventEmitter

I wrote a simple event dispatcher for my application using node's EventEmitter

I have many events and all works fine except for one, I don't know why the promises or callbacks never are completed

This is the code for dispatcher

var EventEmitter = require('events').EventEmitter,
    RequireTree = require('require-tree'),
    _ = require('lodash');

module.exports = {
    init: function(options) {

        var self = this;

        _.extend(options, {
            excludes: []
        });

        if (!options.path) {
            throw new Error('You must specify the `path` option');
        }

        self.Emitter = self.Emitter || new EventEmitter();

        // Require all files in this directory
        RequireTree(options.path, {
            filter: filterModels,
            each: loadModels
        });

        function filterModels(filename) {
            return options.excludes.indexOf(filename) === -1;
        }

        function loadModels(model) {
            Object.keys(model).forEach(function(key) {
                self.Emitter.on(key, model[key]);
            });
        }

        return this;
    }
};

When my application starts I call the dispatcher

dispatcher.init({
    path: __dirname + '/events'
});

The event with issues

events/send_emails.js

var Mandrill = require('mandrill-api/mandrill').Mandrill;

modules.exports = {
  'send:email': function() {
    var mandrill = new Mandrill('apikey', true);
    var message = {
       html: '<h1>Hello email</>',
       from_email: 'info@example.com',
       from_name: "Example",
       subject: "Example mail",
       to: [{
         email: 'my@email.com'
       }],
            headers: {
              'Reply-To': "info@example.com"
            }
    };

    var cb = function(a) { console.log("PRINT SOME", a);  }

    mandrill.messages.send({message: message, async: false, ip_poll: 'Main Pool'}, cb, cb);
  }
};

When my app emits a send:mail event, the function is called, but the PRINT SOME message never is showed in the console

I test the function send:mail in a simple script

test/index.js

var events = require('./events');

events['send:email']();

Calling the command

$ node test/index.js

and WORKS!!!! I saw the message PRINT SOME on the console

I don't understand what is wrong with my code with the event dispatcher

I have other events, they write files, store records on the database and call others APIs without fail

Also, I wrote a rough method using superagent for return promises

var request = require('superagent-bluebird-promise');

request
  .post('https://mandrillapp.com/api/1.0/messages/send.json')
  .send({message: ...}).then(..).catch(...);

the .then nor .catch methods never were called