In Outlook 2013, you can create a contact group that collects the email addresses of the people you specify and then adds them all to the To line when you send an email message to the group.
On the Home tab, click New Contact Group.
Click Add Members.
Type a name for the group.
Choose From Outlook Contacts or From Address Book.
The Select Members dialog box opens.
Select existing contacts by clicking the names of those whom you want to include.
The new members are added to the group listing in the Contact Group dialog box.