Does your signup popups work equally well on mobile?

Signup popups have become a necessity for an online store to get new users. Often ecommerce sites show signup popup immediately after the user lands on their website. Does these traditional popups work equally well on mobile? Are your signup conversions on mobile comparable with signup conversions on desktop?

Mobile usage has surpassed desktop, but ecommerce companies still continue to use the traditional signup popups that asks users to enter their email address. At best, very few of them use responsive mobile-friendly popups that adheres to Google's mobile popup rules. This still doesn't remove the hassle of having to enter the email address on a mobile device or offer an option for users who don't have an email. With increase in mobile commerce, isn't mobile number a better customer identity for your users?