PEAR VS Mailtrain

PHP PEAR is a repository of PHP software code, offering a vast range of packages that extend the functionality of PHP. These packages can help PHP developers streamline their projects by providing ready-to-use components. Before we delve into how to install PEAR packages, make sure your cPanel hosting plan supports PEAR and that you have the necessary permissions to make such installations. Source: 10 months ago

Importing external libraries as dependencies used to be a real pain in PHP. However, one of the most prominent changes in PHP’s maturity came with the release of Composer. Before Composer, PHP used PEAR, which solved the same problem in a more primitive way. - Source: dev.to / over 2 years ago

Listmonk is fantastic -- I use it for the newsletter of my own blog and am amazed by how simple it was to set up and how easy it is to operate and use every time I send out a newsletter. Prior to Listmonk I used Mailtrain[0] and like Listmonk so much I want to run it as a service (with 30% donated back to the Listmonk project of course) -- deliverability worries and initial setup aside it's just the kind of... - Source: Hacker News / over 2 years ago

Never tried but have a look at Mosaico and GrapesJS. Both are open-sourced and used by Mailtrain. Source: about 3 years ago