Redmine

I never used ruby and i don't know if t needs configuring it to send email.

My redmine is working but I cannot get email. I only modified the file email.yml and when I use the test email link in the notifications settings dialog I get "An error occurred while sending mail (435 Unable to authenticate at present )"

My environment is:
- RUBYGEMS VERSION: 1.3.1
- RUBY VERSION: 1.8.6 (2007-03-13 patchlevel 0) [i686-linux]
- INSTALLATION DIRECTORY: /usr/local/lib/ruby/gems/1.8
- RUBY EXECUTABLE: /usr/local/bin/ruby
- EXECUTABLE DIRECTORY: /usr/local/bin
- RUBYGEMS PLATFORMS: - ruby - x86-linux
- GEM PATHS: - /usr/local/lib/ruby/gems/1.8 - /root/.gem/ruby/1.8
- GEM CONFIGURATION: - :update_sources => true - :verbose => true
-:benchmark => false - :backtrace => false - :bulk_threshold => 1000
- REMOTE SOURCES: - http://gems.rubyforge.org/

can anyone help me?
Thanks.