Auto-responder does not send when a new ticket is created. All other email works fine.

Review the Alerts and Notices configuration at https://docs.osticket.com/en/latest/Guides/AlertsGuide.html. New ticket auto-responses are controlled per-department and per-help-topic under Admin Panel > Emails > Templates and Admin Panel > Manage > Help Topics. Ensure 'New Ticket Auto-Response' is enabled for the relevant department/help topic, and that the system email is properly configured with SMTP. Also check Admin Panel > Emails > Settings to confirm email sending is enabled globally.