Agents with permission to delete tickets can delete or mark a ticket as spam themselves. The ticket is permanently removed later, when it is purged, or straight away if you run the clean up manually.
Before you start
You need permission to delete tickets.
To purge tickets straight away, you need admin access.
Delete or mark the ticket as spam
Open the ticket.
Click the Ticket Actions menu.
Choose Delete or Spam.
To do this for several tickets at once, use Mass Actions.
When the ticket is permanently removed
Deleted and spam tickets aren't removed straight away. They stay in the Deleted or Spam status, where you can still restore them. They are permanently purged after the time set in Admin > Tickets > Statuses, under Deleted or Spam.
Remove it permanently now
Go to Admin > Tickets > Statuses.
Open Deleted (or Spam for spam tickets).
Click Run clean up now (or Purge Spam for spam tickets).
💡 Note: This permanently deletes every ticket currently in that status, not only the one you want. Check those tickets before you run it.