Lettr – Email API

Send transactional and marketing emails from your WordPress site using the Lettr email API. Lettr replaces the default WordPress email system with a reliable, developer-friendly API that delivers emails to inboxes — not spam folders.

Why Lettr?

• Reliable email delivery — Built on battle-tested infrastructure with SPF, DKIM, and DMARC authentication out of the box.
• Simple setup — Connect your WordPress site with a single API key. No SMTP configuration needed.
• Transactional email at scale — Send password resets, order confirmations, notifications, and more through the Lettr email API.
• Real-time tracking — Monitor opens, clicks, bounces, and deliverability from the Lettr dashboard.
• Templates & personalization — Use the Lettr drag-and-drop editor and merge tags for dynamic content.
• Developer-first — RESTful API, detailed documentation, and SDKs for PHP, Node.js, Python, Go, Rust, Java, and Laravel.

How it works

This plugin overrides the default WordPress wp_mail() function and routes all outgoing emails through the Lettr API. This means every email your site sends — including emails from WooCommerce, contact form plugins, and any other plugin — is delivered through Lettr automatically.

Links

• Lettr Website
• Documentation
• API Reference

External services

This plugin connects to the Lettr API at app.lettr.com to deliver email on behalf of your WordPress site. Each time wp_mail() is invoked, the plugin sends the following data to Lettr over HTTPS so that Lettr can process and deliver the message:

• The configured sender email address and name
• Recipient, CC, BCC, and Reply-To addresses
• The email subject, HTML and/or plain text body, and any attachments
• Any custom email headers, tags, or metadata supplied by the calling code
• Your Lettr API key (sent as a Bearer token in the Authorization header for authentication)

The plugin also calls app.lettr.com/api/auth/check to validate the API key when you save it on the settings screen.

This service is provided by Lettr. By using this plugin you agree to Lettr’s terms and acknowledge their privacy practices:

• Terms of Service: https://lettr.com/terms
• Privacy Policy: https://lettr.com/privacy-policy