We have an e-mail address that automatically creates a case in our system when someone e-mails to it. However the kind of case that is created is wrong, and also if user is given the choice to e-mail us, without filling out a form, we will always need to ask for more information.

To prevent this, we would like any e-mails that do NOT have the case system prefix in the subject field to bounce back to the sender with information that the user must register a case in our system.

I looked over at the Mail flow -> Rules part, but can only create rules if subject DOES contain a cer

Hi

Paul has a good post about transport rules here:

http://exchangeserverpro.com/exchange-2013-transport-rules/

Thanks for your suggestion, Ed. Appreciated.

The post provided seems more like a general introduction to how transport rules works, and a few examples how to set them up. I am already familiar with this. 

What I am looking for is more specific; How to create a rule that will bounce e-mail if subject does not contain a certain word. If this is possible at all.

Hi,

Please create the following transport rule to have a try:

The rule above would reject all messages which are sent to test (your system email address) except if the subject includes the related case system prefix (please change this to your needed specific keywords). And the original sender would receive a message with the reject explanation that Please register a case in our system. You can change the explanation to what you needed.

Regards,