I think a postmaster filter is the better friend in this case.
It allows regular expressions and thus you can use this match string: regex:^Your order(.*)$
This will not match:
Re: Your order 1234
Fwd: Your order 123
Your Order 123
But will match
Your order
Your order 1234
Tell your filter to set the state right to “closed” and ensure your trigger ignores closed tickets.
Validation proof:
Further information regarding above mentioned functions can be found here: