Building a massive list subscription is a huge task but following this ways will make it a piece of cake for you some free tools that we recommend is privy, mailchimp and hellobar.
1) Spin to win email pop-up
You can build a spin to win pop-up where if you are e-commerce site offer some discount or as a content or blog website give free knowledgeable stuff like e-books, audio books or anything else it will attract huge potential audience and they will be ready to give you their emails. You can create this type of pop-up through free tool like privy
2) Showing them proof
You can make a gif pop-up showing proofs or testimonials about your service using free tools like hellobar It is help user to understand that people whom they are subscribing is already achieved that stage and can put value to them. Here are some examples showing how it work. You can create this type of pop-up through hello bar
3) Creating exclusive podcasts and courses
Giving free stuff attract more people but especially if you give only to those who have subscribed to email list. Also don’t give them all stuff in one email engage them for more than 1 month dialy or weekly.
4) Give them rewards
Give them rewards through giving surveys, contest or any other engaging activities which attract them to come again to site you can give rewards like money, gift voucher, offers or freebies and tell them to share the site with others it will bring more audience. Creative market a well known design marketplace offer 6 freebies per week to attract new customer and also engaging old customers.