Having a rolling list of email I'd is also a way to increase your relationship between you, your traffic and most importantly the public.
Getting emails from your traffic is the best way to follow up your traffic interest and knowing your traffic interest will further help you to come up with better articles to solve their needs.
Also, having a large list of traffic email I'd from other people can also help. That is, you can follow these people up until you convert them to an active member of your site.

Here are ways you can adopt and increase your email contact list by a 100% in a short time.

1. Surveys

Using surveys can greatly increase your site's email list. You would need to make up some vital questions and also try involving your viewers to engage themselves in your surveys. Make sure there's an available space for email input in the survey area. These surveys should also be noted for you to know exactly what your audience wants and serve them better.

2. Ask for email I'd before downloads

This method is widely used around the web today. It has the ability to increase your contact list in a short period of time.
You need to take advantage of the fact that users don't like combing around the web looking for their desired document to download. 

Now, you have a document which users can download freely. Try to enforce the "email first before download".

3. Use of Email I'd generators

You can also find the email generators useful.
Usually this is done when a website is just newly opened.
Although it is used by many, the disadvantage is that, these emails generated are from wide guesses from the generator engine. Some if them are correct while some of them are just rubbish.

Nevertheless, you can use them to generate some email and then create a good contact list also.

4. Pop up messages

Have you ever entered a website where you get a pop up box saying "Email Subscription".
These box are made to get the contact email of their audience and then give them their latest news post through their e-mails.
You can also create a pop-up subscription message and increase your email contact first depending on your audience rate.

(Read; How to create a pop-up subscription email message on Mailchimp)

Lastly,

5. Promo and competition

Who does not like promo gifts and competitions? I guess nobody.
Try out some promo's like gift cards, coupons codes, t-shirts, give-away phones etc.
Make sure you target your priority which is the email collection as you go on.

In conclusion

Hey, I just listed out five possible ways of increasing your email contact list so, why not use the buttons below and share this post amongst your friends.
Also, try using what works for you the most and stick to it.
You should also note that this post would be updated regularly.