What are some alternatives?
When comparing LetsNews.app and Mailtrain, you can also consider the following products
Listmonk - Send e-mail campaigns from a powerful dashboard. High performance and features packed into one app.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
IMAP API - Self hosted and lightweight daemon application
Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES