iPhone works with iCloud, Microsoft Exchange, and many of the most popular Internet-based mail, contacts, and calendar service providers.If you don’t already have a mail account, you can set up a free iCloud account when you first
set up iPhone, or later in Settings > iCloud.
Set up an iCloud account: Go to Settings > iCloud.
Set up some other account: Go to Settings > Mail, Contacts, Calendars.
You can add contacts using an LDAP or CardDAV account, if your company or organization supports it.
You can add calendars using a CalDAV calendar account, and you can subscribe to iCalendar (.ics) calendars or import them from Mail.