Listmonk - Send e-mail campaigns from a powerful dashboard. High performance and features packed into one app.
Clearbit - Clearbit provides Business Intelligence APIs
Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.
InsideView - InsideView aggregates and curates all the company and contact data, news and social insights, and professional connections you need to do business better.