Noptin uses the same method that WordPress uses to deliver its emails. The default email delivery method is to send the email directly via your web server or hosting provider.
The main problem with sending emails via your web server is that most of the emails will be marked as SPAM. In addition, most web hosts impose an email sending limit. This means that you can only a limited amount of emails per hour or day.
As a result, we recommend that you use a specialized email delivery service such as Amazon SES to send your emails.
To send your emails via an email delivery service or SMTP, you first need to create an account with your SMTP service of choice. Finally, install the Easy WP SMTP plugin and use it to connect your new SMTP account to WordPress.