http://hollandonrails.nl/articles/481-config-scoping-important-true Last week I realised that using the config scope in your Rails environment files can be quite important. We had the situation that we needed a different SMTP configuration for different environments. In the environment.rb I found the following lines: <code> Rails::Initializer.run do |config| ... end ActionMailer::Base.smtp_settings = { :address => "127.0.0.1", :port => 25, :domain => "hollandonrails.nl" } </code> For the develoment environment I needed something else, so I proceeded to add the following to development.rb: <code> ActionMailer::Base.smtp_settings = { :address => "mail.google.com", :port => 25, :domain => "bla.com" } </code> But then the emails were not sent in the dev environment. Not knowing the cause, I spent an hour or two figuring this out. Finally, I found out that the ActionMailer settings given in development.rb were not used. Some more investigation revealed the following things: * ActionMailer is not defined within the Rails::Initializer block in environment.rb * Using ActionMailer inside development.rb does NOT raise an error, but the scope of development.rb seems to be the same Rails::Initializer block * Setting ActionMailer settings using config.action_mailer (like below) does allow overriding of these settings <code> config.action_mailer.smtp_settings = { :address => "127.0.0.1", :port => 25, :domain => "hollandonrails.nl" } </code>