In my post on Blogging Newsletters/Email said I would like to present "teasers" instead of the entire text of my posts in email/feeds so that readers would be encouraged to visit the site (something important for those monitizing their sites). Feedburner uses a feature called Summary Burner to accomplish this. To use Summary Burner.
1. Login to Feedburner and click on your feed.
2. Select the Optimize tab (see figure).
3. Select the Summary Burner for the View menu (see Figure)
4. Specify a Maximum Length and Teaser text to be included in your emails (see Figure).
5. Save your changes. Now when users receive your feeds, your text will be truncated based on the maximum length specified.