Automatically prefix email subject with Rails env

One trick I've used across multiple projects to help manage email overload is to add a standard subject prefix to all outgoing emails that contains the specific application/service along with the Rails env for non-production environments (ex: staging, demo, etc).

For example:

# subject for MyApp from staging
[MyApp STAGING] Forgot Password

# subject for MyApp from production
# Rails.env omitted to keep emails pretty for users
[MyApp] Forgot Password

This simple change makes it much easier easier to visually scan incoming emails and even simpler to setup effective email filters. All good things to reduce email overload.

ActionMailer::Interceptor to the rescue

Rails 3.1 and above have a great feature that allow for intercepting all outgoing email and optionally modifying the mail object before it is delivered. I've used a pretty simple interceptor across several projects to add a standard subject prefix and have been very happy with the results.

Now, after several iterations I have finally gotten around to wrapping this behavior up into a standalone gem.

The email_prefixer gem encapsulates this functionality and is absolutely simple to get up and running. Literally bundle install and your done.

Customizing the application name

The email_prefixer gem automatically infers the application name from the Rails application class name, but this can be changed using a standard Rails config initializer.

For example:

# config/initializers/email_prefixer.rb
EmailPrefixer.configure do |config|
  config.application_name = 'MyCompany'
end

Feedback wanted

Are there other customizations that would be useful? I'd love to hear any feedback or suggestions for improvements!

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