Stumbled upon your post from a few years back, and I hope you've found a solution by now!

To send automatic birthday notifications in Laravel 6, you can use Scheduled Tasks along with Laravel's native mail function. Set up a cron job to run every day to check the database for customers whose birthdays are today. Then, use the mail function to send them an email with the reduction offer. PHP 7.2 and Windows shouldn't be an issue; Laravel is quite compatible. By the way, if you or anyone else reading this is managing this kind of customer interaction through a project management tool, you might want to look into Planfix. I recently read about how easy it is to migrate from trello to planfix. The process is smooth, and Planfix offers advanced features like workflow automation.