
LetterStack is an email API designed for developers who want to utilize their own SMTP servers. It supports connections to various SMTP providers, including Gmail, Amazon SES, Zoho, or any self-hosted server. The service allows users to enhance their email capabilities by adding templates, a REST API for sending emails, and detailed logs, all while avoiding the costs associated with managed email providers. This makes it particularly appealing for developers who already have an established SMTP setup and want to add additional functionality without switching providers or incurring extra fees.