The Inbox — Reading the queue
Conversations are ordered by most recent activity. A warm line down the left and a bolder name mean the customer spoke last — nobody has answered yet. Needs reply, under the tabs, shows only those, and it combines with whichever tab you are on.
An internal note deliberately does not clear that state: writing a note to your team is not the same as answering the customer, and the queue would be lying if it said otherwise. Notes are prefixed Note: in the preview so an internal remark is never mistaken for something the customer was told.
An email to anybody other than the customer doesn't clear it either. The reply box can email anyone, so a message to a supplier about the customer's order lands on the ticket too, and the customer is still waiting. Its preview starts To and the address it went to.