Did you restart your mongrel(s)? Environment is loaded at startup. If you don’t want to send mails in development, there’s a parameter in the environment variables for that too.
Agile Web Development with Rails, Second Edition, buy the PDF version and you’ll have all the info you need a few minutes later. You should also check the wiki (and hope the info isn’t outdated): http://wiki.rubyonrails.org/rails/pages/ActionMailer
If SMTP server is not specified in environment.rb or helper,
ActionMailer defaults to localhost's smtp agent. That's why the email
still gets sent out. There aren't too many up to date tutorials out
there and with ActionMailer, I found too many subtle changes from
versions.