Def_Newsletter is a project mainly written in PHP and SCHEME, based on the MIT license.
A SilverStripe newsletter module
Download and install Def_Mailtools. Be sure to configure the sendgrid details (see the example in this module).
Download and install DataObjectManager.
Drag Def_Newsletter into your SilverStripe site and run dev/build.
This is very much a work in progress. I advise to only use it to test it out at the moment. It works but needs some more work to get it to a 0.1 status.
Also note that I am thinking of changing the way the module works. With a custom backend interface instead of using pages in the sitetree.