Net::SMTPAuthenticationError

I got following error while trying to send mail using action mailer in
ruby on rails. Could anybody please give me the solution for this.

Net::SMTPAuthenticationError in LoginController#add_user

503 you are already authenticated

RAILS_ROOT: ./script/…/config/…
Application Trace | Framework Trace | Full Trace

d:/ruby/lib/ruby/1.8/net/smtp.rb:577:in auth_plain' d:/ruby/lib/ruby/1.8/net/smtp.rb:571:insend
d:/ruby/lib/ruby/1.8/net/smtp.rb:571:in authenticate' d:/ruby/lib/ruby/1.8/net/smtp.rb:411:indo_start’
d:/ruby/lib/ruby/1.8/net/smtp.rb:378:in start' d:/ruby/lib/ruby/1.8/net/smtp.rb:316:instart’
d:/ruby/lib/ruby/gems/1.8/gems/actionmailer-1.2.5/lib/action_mailer/base.rb:511:in
perform_delivery_smtp' d:/ruby/lib/ruby/gems/1.8/gems/actionmailer-1.2.5/lib/action_mailer/base.rb:397:insend’
d:/ruby/lib/ruby/gems/1.8/gems/actionmailer-1.2.5/lib/action_mailer/base.rb:397:in
deliver!' d:/ruby/lib/ruby/gems/1.8/gems/actionmailer-1.2.5/lib/action_mailer/base.rb:322:indeliver’
#{RAILS_ROOT}/app/controllers/login_controller.rb:22:in `add_user

regards
Senthil