HitPay - Send or receive money using a modern payments interface

Listmonk - Send e-mail campaigns from a powerful dashboard. High performance and features packed into one app.

Unlock - Monetize your content with a few lines of code

Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES

Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.

Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates