---
type: Guide
title: Rails integration (euromailing-rails)
description: The euromailing-rails gem — ActionMailer delivery method for transactional mail, contact/list client, Syncable concern for mirroring users, ActionMailbox inbound.
resource: https://github.com/rogerheykoop/euromailing-rails
tags: [rails, gem, actionmailer, sync]
timestamp: 2026-07-06T00:00:00Z
---

# Rails integration: the euromailing-rails gem

Source & full README: https://github.com/rogerheykoop/euromailing-rails
(MIT, Ruby ≥ 3.1, no runtime dependencies beyond what Rails ships).

```ruby
# Gemfile
gem "euromailing-rails", github: "rogerheykoop/euromailing-rails"
```

```ruby
# config/initializers/euromailing.rb
Rails.application.config.euromailing.api_key =
  Rails.application.credentials.dig(:euromailing, :api_key)
```

## 1. Transactional mail through ActionMailer

```ruby
# config/environments/production.rb
config.action_mailer.delivery_method = :euromailing
```

Existing mailers work unchanged. The `from:` must be on the API key's
bound sending domain. One recipient per message; prefer `deliver_later`
(the API allows 60 requests/minute per key).

## 2. Contacts & lists

```ruby
client = Euromailing.client
client.upsert_contact(email: "jan@example.com", first_name: "Jan")
client.delete_contact(email: "jan@example.com")
client.subscribe(list_id: "LIST-UUID", email: "jan@example.com")
client.unsubscribe(list_id: "LIST-UUID", email: "jan@example.com")
```

Errors raise `Euromailing::ApiError` with `#status` and `#code`
(codes documented in [the API reference](../api/index.md)).

## 3. User sync

```ruby
class User < ApplicationRecord
  include Euromailing::Syncable
  euromailing_sync lists: ["NEWSLETTER-LIST-UUID"], if: ->(u) { u.newsletter? }

  def euromailing_contact_attributes
    { email: email, first_name: first_name, last_name: last_name,
      custom_fields: { plan: plan } }
  end
end
```

Creates/updates upsert the contact and subscribe the configured lists;
destroys delete it — all via `Euromailing::SyncJob` (ActiveJob, retries
with backoff, 404-on-delete counts as success).

## 4. Inbound mail

See [Inbound to ActionMailbox](inbound-actionmailbox.md).