Net::SMTPFatalError in OpinionController#invite

555 5.5.2 Syntax error. 34sm2390626nfu.4
RAILS_ROOT: /Users/teamon/Sites/my_app

Application Trace | Framework Trace | Full Trace
/opt/local/lib/ruby/1.8/net/smtp.rb:680:in `check_response'
/opt/local/lib/ruby/1.8/net/smtp.rb:653:in `getok'
/opt/local/lib/ruby/1.8/net/smtp.rb:635:in `rcptto'
/opt/local/lib/ruby/1.8/net/smtp.rb:546:in `send0'
/opt/local/lib/ruby/1.8/net/smtp.rb:545:in `each'
/opt/local/lib/ruby/1.8/net/smtp.rb:545:in `send0'
/opt/local/lib/ruby/1.8/net/smtp.rb:472:in `sendmail'
/opt/local/lib/ruby/gems/1.8/gems/actionmailer-2.0.2/lib/action_mailer/base.rb:588:in `perform_delivery_smtp'
/opt/local/lib/ruby/1.8/net/smtp.rb:379:in `start'
/opt/local/lib/ruby/1.8/net/smtp.rb:316:in `start'
/opt/local/lib/ruby/gems/1.8/gems/actionmailer-2.0.2/lib/action_mailer/base.rb:586:in `perform_delivery_smtp'
/opt/local/lib/ruby/gems/1.8/gems/actionmailer-2.0.2/lib/action_mailer/base.rb:469:in `__send__'
/opt/local/lib/ruby/gems/1.8/gems/actionmailer-2.0.2/lib/action_mailer/base.rb:469:in `deliver!'
/opt/local/lib/ruby/gems/1.8/gems/actionmailer-2.0.2/lib/action_mailer/base.rb:352:in `method_missing'
app/models/opinion.rb:75:in `send_invitation'
app/controllers/opinion_controller.rb:19:in `invite'