iPhone App- What does the envelope icon do on a coworkers name?

When logged into your app and looking at the roster for the day, you can select a coworkers name and 4 different contact method icons will appear.

The third icon will be an envelope representing an email.

If you coworker has an email address associated with their account, upon selecting this icon, you will be brought out of the application and into your email. A blank email will be drafted with your selected coworker's email address present.

If this option is grayed out, your coworker does not have an email address associated with their Hotschedules account.