Rails 3 Setting Up Action Mailer - ruby-on-rails-3

Question

Everything was going so well...
gem 'mail' is installed
enter > $ rails g scaffold user name:string email:string
enter > $ rake db:migrate (fine I can see it on http://localhost:3000/users/new) then...
enter > $ rails g mailer user_mailer
On this command I get this huge error - what is it and how do I resolve it?
Users/mailer_app/config/initializers/setup_mail.rb:14: uninitialized
constant DevelopmentMailInterceptor (NameError)
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/engine.rb:201
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/engine.rb:200:in `each'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/engine.rb:200
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/initializable.rb:25:in `instance_exec'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/initializable.rb:25:in `run'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/initializable.rb:50:in `run_initializers'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/initializable.rb:49:in `each'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/initializable.rb:49:in `run_initializers'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/application.rb:134:in `initialize!'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/application.rb:77:in `send'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/application.rb:77:in `method_missing'
from /Users/liam_carey/Documents/Aptana Studio 3 Workspace/mailer_test/config/environment.rb:5
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/application.rb:103:in `require'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/application.rb:103:in `require_environment!'
from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.5/lib/rails/commands.rb:16
from script/rails:6:in `require'
from script/rails:6
user:mailer_app $

Answer 1

Here is the contents of my config/initializers/setup_mail.rb
Am using Heroku and Sendgrid and have installed the plug-in.
Did I need to install the 'mail' gem first, the documentation doesn't mention it??
ActionMailer::Base.smtp_settings = {
:address => "smtp.sendgrid.net",
:port => "25",
:authentication => :plain
:user_name => "apxxxxx#heroku.com",
:password => "9XXXXXXXXX",
:domain => "www.myapp.com",
}
I know what the issue is now - there is no comma after the user-name and password entries!