Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES
Substack - Substack makes it simple for a writer to start an email newsletter that makes money from subscriptions.
Mailtrain - Self-hosted open-source Mailchimp clone
IMAP API - Self hosted and lightweight daemon application
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Supscrib for Business - Build engaging newsletter & save on email costs