WP Mailster - WP Mailster enables you to run a listserv-like email discussion list on your WordPress site.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Listeron - An email address for your group. Discuss. Debate. Organise. All with email.
Brevo - Innovative online Email Marketing solution to manage your contacts, create & send your newsletters and track your results. More than 80 000 clients. Best prices and attractive features.
Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.