This article shows an example of results on the iPhone after synchronizing with a mailbox that has a complex subfolder structure.
This screenshot shows an example folder structure in Outlook:
Under Mail on
Under Calendar on the iPhone, you can see all the calendar folders and subfolders in one list. Each calendar has its own color. You can choose to view one calendar or events from all calendars. To view events from all calendars, tap All. You will see appointments displayed in the color that corresponds to each folder's individual color.
Similarly to calendars, the Contacts application syncs all the folders and subfolders and shows them all in one list. Clicking on All Contacts shows all the contacts from all folders and subfolders in one list.
If you click the email address right below the Groups label, you can perform a lookup in the company address book (Global Address List, or GAL).