For us it would be really helpful to be able to make sure the mails sent to our receivers e-mail address are only sent to that address (with optionally other recipients in the CC). This would ensure that if one in the CC answers to all (and thus also to the receiver's address), I can block the creation of a duplicate ticket.
Suggested criteria: number of TO-recipients
The rule would thus look like this:
* To email header - is not - firstname.lastname@example.org
* Number of To-recipients - greater than - 1
* Reject email (with email response)
Customer support service by UserEcho