Free Version of MailPoet WordPress Plugin and MailPoet Premium Addon
There is a free version of MailPoet available in the official WordPress repository at https://wordpress.org/plugins/wysija-newsletters/ which pretty much does most of the stuff in a very reliable way.
Some features are limited and only available in the MailPoet Premium Version, e.g. sending newsletters to more than 2000 subscribers, getting a beautiful statistics dashboard to compare your newsletters, detailed stats for each subscriber and newsletter, an automated bounce handling that helps you keep your subscribers’ list clean, a spam score analyzer that can be used before sending a newsletter to your subscribers and improved deliverability with DKIM signature.
If you want all features of MailPoet Premium, you need to get a support license which basically gives you some additional code that needs to be installed next to the free version of MailPoet and which checks your license every now and then to charge you again when the license runs out.
To allow you to run MailPoet Premium for free we had a look at the code and put together some simple step-by-step instructions on how to use the plugin without a license.
