MailChannels Email API Ruby client

Published on RubyGems as mailchannels-email-api. This repository is the public development source. Support: dev@mailchannels.com. Report reproducible bugs through this repository’s issues.

This Ruby 3.2+ client calls the current MailChannels Email API directly with an API key. It accepts the API's full send payload, including personalizations, plain text or HTML content, attachments, and custom headers. It does not need a Cloudflare Worker. It is a sending client, not an Action Mailer delivery backend.

Install the gem:

gem install mailchannels-email-api

Provide MAILCHANNELS_API_KEY through your environment or secret store. Configure your sender domain and use an allowed recipient. The free plan permits 100 emails/day and restricts recipients to verified account users until a payment method is added.

require 'mailchannels/email_api'

client = MailChannels::EmailAPI::Client.new
message = {
  from: { email: ENV.fetch('MAILCHANNELS_SENDER') },
  personalizations: [
    { to: [{ email: ENV.fetch('MAILCHANNELS_RECIPIENT') }] }
  ],
  subject: 'MailChannels Ruby validation',
  content: [{ type: 'text/plain', value: 'Validate this message without sending.' }]
}

result = client.validate_email(message)
puts result.validated? # HTTP 200, no email sent

To send deliberately, call client.send_email(message). An HTTP 202 result has accepted? == true; it means accepted for processing, not delivered. A dry run is HTTP 200 and never reports acceptance. Unexpected statuses, including redirects, raise MailChannels::EmailAPI::APIError with a status attribute.

Payloads use the API's JSON schema without shorthand conversion. Both string and symbol Hash keys serialize to JSON keys. See the API documentation for attachment encoding and other supported fields.

The client opens and closes an HTTPS session per call. TLS peer verification is enabled. Connect timeout is 10 seconds; read and write timeouts are 30 seconds each. These are I/O timeouts, not a total request deadline. It does not follow redirects, use environment proxies, or automatically retry requests.

An ambiguous transport failure can occur after the server accepts a message. Check delivery records before retrying. TransportError has a sanitized message and does not retain the underlying exception as its cause. API error messages contain the HTTP status rather than response bodies. Client inspection redacts the API key; application code should also avoid logging requests or payloads.

Ruby argument/JSON serialization errors propagate to the caller before network I/O. Use a separate client for each account's key. In Rails, call this client from your application service or job; it does not change ActionMailer settings.

bundle install
bundle exec ruby -Ilib -e 'Dir["test/*_test.rb"].sort.each { |file| require_relative file }'
gem build mailchannels-email-api.gemspec

Unit tests replace the HTTP session; six native transport tests use a local TLS server with synthetic credentials and messages. They exercise the real Net::HTTP transport, preserve API hostname verification, and route only the expected API socket to loopback. Native tests cover empty 202, dry-run 200, untrusted CA, hostname mismatch, redirects, HTTP errors and disconnect after receipt. No real API request or email is sent. These checks do not replace separately authorized provider validation. See RELEASING.md for the release gates. Bundler may compile the json dependency; development containers need a C compiler and make (for example, Debian's build-essential package).