How to Collect Emails of My Readers in my WordPress site?

I am planning to build an email list to send them post notifications, offers, etc. So, how can I create a form or field where users can simply enter their email address and subscribe? Later I should be able to collect them and use them for the future purposes.

If there are no free tools available, I am also ready to pay small amounts to the paid services (good ones only.) So, also suggest such services too, only if you have personal experience with it. Expecting an answer soon from this great community.

Simply use the Subscription widget coming with the Jetpack plugin. Whenever the user subscribes to your website, they will be added to your subscribers list.

You can view them by going to Dashboard > Jetpack > Settings > Discussion > “Subscriptions” section > “View your email followers.”