E-mails can be copied to multiple addressees using the CC (carbon copy) and the BCC (blind carbon copy) fields. The CC and BCC can contain any set of addresses from collections, several related attributes and constant addresses. There are no restrictions in those fields. For further information about how to include multiple addresses please refer to Send E-mail to multiple recipients
The e-mail can also be sent to the Activity's current assignees. In order to do this, check the Copy to current assignee box. The message will be delivered to the address in the To field and a copy will be sent to the current assignee.