const mailerRequest = pify(mailer.request)

router.post("/", ({ body: { email }, res) => {
  mailerRequest(email, 'email.index.html')
    .then(() =>
      new User({ email })
      .save(err => err ? console.error(error) : console.log('success'))
    )
    .catch(e => res.sendStatus(400))
  })