Redmine

Requirements: when the message create issue, the message subject is or not repeated for issue list
Now the development progress:
1.The script successfully with imap
（ rake -f /opt/redmine/web/Rakefile redmine:email:receive_imap RAILS_ENV="production" host=imap.foo.bar username=xxx@foo.bar password=xxxxxx allow_override=tracker）
2.It has been found '/opt/redmine/lib/redmine/imap.rb' file (Only read about)

The question now is:
1.when the message create issue, where is call the method code for create issue
2.I want modify about mothod code

I'm English is not good ,I'm sorry

Thank you