Often asked from my customers and the simple answer YES.
The sending of a notification from the Enterprise Manager or Cloud Control requires a Diagnostic Pack license for the target system.
You can check the license information where notifications are listed under the Diagnostic Pack. If you are having several Databases under your Enterprise Manager check the MOS Note: How to Explain that Notifications Are Sent Even If the Diagnostic Pack Is Disabled for the Target ? [ID 947827.1]
So be carefull when you configure a mail notification in you monitoring.