I had a bug in my TTT Rails app. When I try to send out email, I get

NameError: ActionMailer is not missing constant Base!
  load_missing_constant at /Users/ckim/.rvm/gems/jruby-1.7.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:494
          const_missing at /Users/ckim/.rvm/gems/jruby-1.7.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:192

It turns out that at one point I created a mailer called mail.

# don't do this

$ rails g mailer mail

Once I deleted that file (app/mailers/mail.rb), my email starting working again.