Replying, and closing a card

Reply on the card page, or simply reply to any mail the card has sent you. Both land in the same place, so nobody has to sign in to continue a conversation that started in their inbox.

When the matter is settled you can stamp the card closed yourself. Writing on a closed card reopens it, so nothing is lost by closing something that turns out not to be finished.

If a reply did not actually answer your question, say exactly that. A card that is reopened with what is still wrong is more useful to us than a new card that starts the story again from the beginning.