Our email to case is not working whereby the emails are appearing in outlook but they are not generating a case in Salesforce. What might be the reason?

We create our cases from an Outlook mailbox.  Is there a way for an email to be generated to the Contact - giving the case # etc? 

We haven't been able to figure out how to do this, so our work-around is to go in and edit and save the case - and then check the "Send notifcation email to contact" checkbox.