Yahoo internal bounces


I have noticed an increase of Yahoo Internal Bounces with the error message "dd Requested mail action aborted..."
Authoritarian sources on internet says that those are inactive addresses and must be removed from list.
To treat them as Hard Bounces, under 'bounceType' => BounceHandler::BOUNCE_HARD, I have added this expression:
'/dd Requested mail action aborted/i',

Is this expression correct? Because they are still treated as Internal bounces.
I don't think this should be a hard bounce. It should be an internal bounce which should be retried.
I have several lists.
I have removed them manually from one list. And this list is not receiving that error anymore.

I wish to tread them as Hard Bounces on my own choice.
The full SMTP error is:
Error: "554 delivery error: dd Requested mail action aborted -" while connected from ( to (
Is this expression '/dd Requested mail action aborted/i' correct, please?