Do read receipts work for closed tickets?

No, read receipts do not work for closed tickets. Once a ticket is marked as “Closed” in Zendesk, no further updates—including read receipt tracking—are processed by Zendesk or third-party apps. To ensure read receipts are captured, tickets must be in an open state such as “Open,” “Pending,” or “On-Hold” at the time the recipient opens the email.

If you need to track whether a message was read, make sure the ticket is not closed when the recipient receives and opens the email.