If you need to send an email and know the recipient's address, you can use the quick agent email page without searching for the contact. Type the email address of the recipient and use the mailing list picker to populate a CC line if needed. If the email address doesn't exist in iService, a new contact will be created. If the email address already exists for a contact in iService, your email will be added to the contact's history. The group lists are administered from a separate menu in the Custom Forms Admin section of iService (Manage Agent Email).
The Quick Agent Email page won't work until it's been configured by your iService administrator.