Send notification email on new comment for users that flag content

I installed flag module and created new flag on "Forum topic" content type. Idea was to send notification email to all users that are subscribed(flagged) on specific topic (node) when new comments are posted.
This looks pretty simple ...but after whole afternoon I could not find solution, also couldn't find any help on net. Flag works ok, but I can't create rule that will send emails.
Best I can get, is shown on attached image. I know that last action "Send HTML e-mail" .. should use "Parameter: Key: [list-items:mail] ... but I don't have list-item token in "Send HTML e-mail" action. Looks like list passed in to Loop is not good.
Can anyone help me with this?