You can add emails as tasks either by linking to them - for that you need one of our browser plugins and the Outlook plugin or, you can forward your mails directly to Todoist which will convert them to tasks.
We've described both options on our blog: http://todoist.com/blog/2013/01/zero-inbox-policy-with-todoist/
To find out more about the first option, please check these videos showing how it works:
- In Outlook: https://www.youtube.com/watch?v=muSIVBiV71I&list=PL2EEC42CE38B0AF8E&index=7
- In Chrome: https://www.youtube.com/watch?v=TfslbgUv4F4&list=PL2EEC42CE38B0AF8E&index=19