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.
Customer.io - We make it easy to send emails triggered by user behavior. Build, measure and improve your emails to activate and retain users
SendGrid - Learn why more developers choose SendGrid for their email deliverability service to send transactional emails triggered by web apps. Get started for free
HubSpot - Grow Better With HubSpot: Software that's powerful, not overpowering. Seamlessly connect your data, teams, and customers on one CRM platform that grows with your business.
EmailJS - Send email directly from your client-side Javascript code – no server side code required. Add static or dynamic attachments, dynamic parameters, captcha code and more. Start with our free tier!
If No Reply - Simple email automation that works for Gmail