Service Desk should recognise it's being included in an Email Thread

At the moment if Service Desk is included in the to field of an email thread, each reply will generate a new ticket in Service Desk.

Steps to reproduce

1. As a Service Desk Customer, write a new email to User1 and ServiceDesk email.
   • User1 should be an agent
2. As User1 now reply to the email received from the Customer, include the same Service Desk email. (ie. Reply to All)
3. As Customer reply to this thread once more using Reply to All.
   Result
   Three tickets will be created in Service Desk, each with the email body.