How to save up to 500€/year switching from Mailchimp to Open Source Mailtrain and AWS SES (en)

My newsletter Le Courrier du hacker (3,800 subscribers, 176 issues) is 3 years old and Mailchimp costs were becoming unbearable for a small project ($50 a month, $600 a year), with still limited revenues nowadays. Switching to the Open Source Mailtrain plugged to the AWS Simple Email Service (SES) will dramatically reduce the associated costs. …