AhaSend is a pay-as-you-go Transactional Email Service Provider.

AhaSend is an independent Email Service Provider (ESP) specializing in transactional emails. Our services are designed to ensure that your transactional emails are delivered quickly, reliably and efficiently. We believe that pricing should be simple and clear: AhaSend is free for up to 1,000 emails per month, and then you pay for what you send ($0.50 per 1,000 emails) - No bracket prices, no recipient limits. At AhaSend, we specialize in sending transactional emails and therefore we can offer far better delivery times than other ESPs that mix marketing and transactional emails: Bulk marketing emails are slow to send, and sending a bulk marketing email means that email services such as Gmail, Yahoo and Outlook suddenly see millions of emails coming in from the same IP address or domain within a short period of time, and will delay delivering them to the inbox. At AhaSend we don't allow marketing emails to be sent with our service, letting us optimize our servers and infrastructure for delivery time rather than large volume sending.
Farhad Hedayatifard

Founder of AhaSend, Taskulu, WishMerge, and a few more ;)