Twenty-eight days after a ticket is submitted as Solved, the ticket moves to a Closed status. I would expect the ticket to stay Solved until I manually close it. Why is this happening?
Zendesk Support comes with an automation called Close ticket 4 days after status is set to solved. This automation gives end-users 4 days to respond to a solved ticket before the ticket moves to closed status. You can set this automation to run anywhere between 1 hour and 28 days.
Best practice guidelines recommend that you leave a ticket in solved status for 3-5 days before moving to closed. This allows end-users to re-engage with you in the same ticket.
If you deactivate the Close ticket 4 days after status is set to solved automation, your solved tickets will be set to closed by a system action (noted in your events and notifications as a "batch close") after 28 days in solved status (see About the inborn system ticket rules for more information).
After 120 days of being Closed, tickets are automatically archived (see About ticket archiving). Archiving tickets speeds up the loading time for views, especially those views that include multiple tickets which have been closed for a long period of time (see Using views to manage ticket workflow).