problem with ActionMailer/SMTP

hi, i'm trying to make the user account confirmation work in my site,
but i couldn't fix this error,

Processing UsersController#create (for 189.85.180.50 at 2009-09-23
16:44:30) [POST]
  Parameters: {"commit"=>"Criar novo usuário",
"authenticity_token"=>"UX+z7gZGHLo5+1LkW0duFvu69YiHC7H0baMY/Sbtyi8=",
"user"=>{"password_confirmation"=>"paulogeyer",
"password"=>"paulogeyer", "login"=>"paulo",
"email"=>"paulogeyer@gmail.com"}}
Sent mail to paulogeyer@gmail.com

ArgumentError (wrong number of arguments (3 for 2)):
  /usr/lib/ruby/1.8/net/smtp.rb:525:in `start'
  app/models/user_observer.rb:3:in `after_create'
  /usr/lib/ruby/1.8/observer.rb:185:in `notify_observers'
  /usr/lib/ruby/1.8/observer.rb:184:in `each'
  /usr/lib/ruby/1.8/observer.rb:184:in `notify_observers'
  app/controllers/users_controller.rb:19:in `create'
  /usr/lib/ruby/1.8/phusion_passenger/rack/request_handler.rb:95:in
`process_request'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_request_handler.rb:
207:in `main_loop'
  /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:
378:in `start_request_handler'
  /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:
181:in `spawn_application!'
  /usr/lib/ruby/1.8/phusion_passenger/utils.rb:183:in `safe_fork'
  /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:
153:in `spawn_application!'
  /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:272:in
`spawn_rails_application'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_server_collection.rb:
80:in `synchronize'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_server_collection.rb:
79:in `synchronize'
  /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:255:in
`spawn_rails_application'
  /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:154:in
`spawn_application'
  /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:287:in
`handle_spawn_application'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in
`__send__'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in
`main_loop'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in
`start_synchronously'
  /usr/lib/phusion_passenger/passenger-spawn-server:61

Rendering /var/www/100empresas/public/500.html (500 Internal Server
Error)

here follows the code

user_observer.rb line #3

2: def after_create(user)
3: UserMailer.deliver_signup_notification(user)
4: end

users_controllers line #19

18: @user = User.new(params[:user])
19: @user.register! if @user && @user.valid?
20: success = @user && @user.valid?

and my email configuration from environment.rb

  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    :address => "smtp.gmail.com",
    :port => 587,
    :authentication => :plain,
    :domain => "empreendedor.com.br",
    :user_name => "****@empreendedor.com.br",
    :password => "****"
  }

any ideas? It is quite obscure to me