Swoosh or Bamboo for sending emails in Elixir?

Swoosh offers a more extensive adapter ecosystem and built-in testing tools, while Bamboo is lighter but may require more manual setup for certain providers. Choose Swoosh for comprehensive features and Bamboo for minimalism in simpler projects.

How to send emails asynchronously with Swoosh?

Swoosh doesn't provide async out-of-the-box; you need to wrap the deliver call in an Elixir Task supervised by Task.Supervisor or use job queues like Oban. This ensures non-blocking delivery but requires manual error handling.

How to test email delivery in Phoenix tests using Swoosh?

Set the mailer adapter to Swoosh.Adapters.Test in config/test.exs and use Swoosh.TestAssertions to assert emails were sent. For feature tests, use Swoosh.Adapters.Sandbox for async-safe email delivery across processes.

Does Swoosh support HTML email templates?

Swoosh doesn't include a templating engine; you compose HTML bodies manually via html_body/2 or integrate with libraries like Phoenix.HTML or EEx. It focuses on delivery and composition, not template management.

How to preview emails in browser during development with Swoosh?

Configure the adapter to Swoosh.Adapters.Local in dev, then use Plug.Swoosh.MailboxPreview in Phoenix routes or start a separate mailbox server with mix swoosh.mailbox.server. This requires additional setup for non-Phoenix apps.

What HTTP clients can I use with Swoosh adapters?

Swoosh supports Hackney by default, but can be configured to use Finch or Req via the Swoosh.ApiClient behaviour. You can also disable it for SMTP adapters or implement a custom client, adding flexibility but setup steps.

Open-Awesome

swoosh

MITElixirv1.26.3

A comprehensive Elixir library for composing, delivering, and testing emails with support for multiple adapters.

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1.5k stars257 forks0 contributors

What is swoosh?

Swoosh is an Elixir library that provides a complete solution for sending, composing, and testing emails in Elixir applications. It solves the problem of integrating with various email service providers by offering a unified API with adapters for services like SendGrid, Mailgun, and SMTP, while including first-class testing utilities.

Target Audience

Elixir developers building web applications (especially with Phoenix) that need reliable email delivery, testing, and multi-provider support without vendor lock-in.

Value Proposition

Developers choose Swoosh for its elegant Elixir API, extensive adapter ecosystem, built-in testing tools, and seamless integration with Phoenix and OTP, making email handling both robust and enjoyable.

Overview

Compose, deliver and test your emails easily in Elixir

Use Cases

Best For

Adding transactional email (welcome emails, notifications) to Phoenix applications
Switching between email service providers (e.g., SendGrid to Postmark) without code changes
Testing email flows in unit, integration, and E2E tests with dedicated adapters
Previewing emails in development via a built-in browser mailbox
Sending emails asynchronously using Elixir's Task or job queues like Oban
Handling email attachments from file paths, Plug.Upload, or custom structs

Not Ideal For

Applications running on Elixir versions older than 1.16 or OTP older than 26, due to strict version requirements.
Teams needing a graphical email builder or WYSIWYG editor integrated directly, as Swoosh focuses on code-based composition.
Projects requiring out-of-the-box email analytics dashboards or advanced tracking features, since Swoosh provides telemetry but not a full analytics suite.

Pros & Cons

Pros

Extensive Adapter Support

Includes adapters for over 20 email services like SendGrid, Mailgun, and SMTP, allowing seamless provider switching without code changes, as listed in the README's adapter table.

Functional API Design

Uses a fluent, composable Elixir API for building emails with attachments, HTML/text bodies, and custom headers, aligning with Elixir's functional programming strengths.

Robust Testing Utilities

Provides dedicated adapters for unit tests (Test), async-safe tests (Sandbox), and local development previews, simplifying email testing across different environments.

Telemetry Integration

Emits events for email delivery start, stop, and exceptions, enabling monitoring and debugging in production, as documented in the Telemetry section.

Cons

Manual Async Handling

Lacks built-in async email delivery; developers must implement it manually using Task supervisors or external job queues like Oban, adding boilerplate and potential failure points.

Dependency Management Complexity

Requires additional dependencies for some adapters, such as gen_smtp for SMTP, and careful configuration of HTTP clients, which can complicate setup and maintenance.

Preview Setup Overhead

The mailbox preview feature needs extra configuration, especially in non-Phoenix applications, and may require adding web server dependencies like plug_cowboy or bandit.

Frequently Asked Questions

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