Crow.app - Pricing and experimentation tools for Stripe
Amazon SES - Scale your business email & marketing messages with Amazon Simple Email Service (SES), a cost-effective and reliable cloud email service. Sign up today.
Mailgun - A set of powerful APIs that enable you to send, receive and track email from your app effortlessly whether you use Python, Ruby, PHP, C#, Node.js or Java.
SMTPProvider - SMTPProvider offers SMTP server with a mailing software for mass promotional & transactional emailing.
Stripe for Gmail - Display customers Stripe information within inbound emails
Aritic Mail - Ariticmail is a transactional email delivery API for applications and enterprises.