KingSMTP (formerly known as Kingmailer, founded in 2017) is an SMTP service designed for sending transactional emails. It is a cost-effective alternative to other SMTP providers like Sendgrid and Mailgun, focusing on delivering transactional emails rather than mass or bulk mail. Kingmailer is particularly known for its affordability, offering plans starting at $5 per month or $49 per year, which include features such as a clean IP address, inbound email routing, email dashboard, email API, and a 99.99% uptime guarantee.
The service supports Bitcoin, Ethereum, Dogecoin, PayPal, and major credit and debit cards for payment. Users can start with a 14-day free trial without needing a credit card. Kingmailer requires domain verification, including adding SPF and DKIM records, to ensure secure and reliable email delivery. It is compatible with platforms like WordPress and has its own WordPress plugin for easy integration.