Protractor Fetching Email with Mail Listener: TypeError: deferred.fulfill is not a function

element.all(locator).map(function(elm, index) {
  // Get the value you are interested in finding and return the element too.
  return {
    elm: elm,
    text: elm.getText(),
    index: index
  };
}).then(function(list) {
  // Find your text here. Otherwise fail.
  for(var i = 0; i<list.length; i++) {
    if(list[i].text === name) {
      return list[i].elm;
    }
  }
  throw new Error('Solution not found');
}).then(function(elm) {
  // Perform an action on the element you found.
  elm.click();
});

npm install mail-listener2 --save-dev

onPrepare: function () {
    var MailListener = require("mail-listener2");

    // here goes your email connection configuration
    var mailListener = new MailListener({
        username: "imap-username",
        password: "imap-password",
        host: "imap-host",
        port: 993, // imap port 
        tls: true,
        tlsOptions: { rejectUnauthorized: false },
        mailbox: "INBOX", // mailbox to monitor 
        searchFilter: ["UNSEEN", "FLAGGED"], // the search filter being used after an IDLE notification has been retrieved 
        markSeen: true, // all fetched email willbe marked as seen and not fetched next time 
        fetchUnreadOnStart: true, // use it only if you want to get all unread email on lib start. Default is `false`, 
        mailParserOptions: {streamAttachments: true}, // options to be passed to mailParser lib. 
        attachments: true, // download attachments as they are encountered to the project directory 
        attachmentOptions: { directory: "attachments/" } // specify a download directory for attachments 
    });

    mailListener.start();

    mailListener.on("server:connected", function(){
        console.log("Mail listener initialized");
    });

    global.mailListener = mailListener;
}),

onCleanUp: function () {
    mailListener.stop();
}, 

function getLastEmail() {
    var deferred = protractor.promise.defer();
    console.log("Waiting for an email...");

    mailListener.on("mail", function(mail){
        deferred.fulfill(mail);
    });
    return deferred.promise;
};

describe("Sample test case", function () {

    beforeEach(function () {
        browser.get("/#login");
        browser.waitForAngular();
    });

    it("should login with a registration code sent to an email", function () {
        element(by.id("username")).sendKeys("MyUserName");
        element(by.id("password")).sendKeys("MyPassword");
        element(by.id("loginButton")).click();

        browser.controlFlow().await(getLastEmail()).then(function (email) {
            expect(email.subject).toEqual("New Registration Code");
            expect(email.headers.to).toEqual("myemail@email.com");

            // extract registration code from the email message
            var pattern = /Registration code is: (\w+)/g;
            var regCode = pattern.exec(email.text)[1];

            console.log(regCode);

         });
    });
});

browser.s2.util.unzip = function(report){
    return report.then(function(report){
        return new Promise(function(resolve, reject){
            try{
                // reading archives
                var zip = new AdmZip(report);
                var zipEntries = zip.getEntries(); // an array of ZipEntry records
                zipEntries.forEach(function(zipEntry) {
                    zipEntry.d =  zip.readFile(zipEntry);
                });
                resolve(zipEntries);
            }catch(err){
                reject(err);
            }
        })
    });
};