Hendel,

Instead of sending a Custom Email message to the Custom address have you attempted to create a message template instead?

The thing with Outlook rules, functionality is limited. I attempted to create a test rule using my Outlook 2010 and was succesful in generating as rule that was received from a specific recipient and replied using a template..

Since you want a general message sent to the reciepeint try altering Send New message with send message template or corresponding rule parameter.

Hope This helps.