auto-answer; automatic answering
Computing term for a system that answers calls, messages, or requests without human intervention.
This phone has an auto-answer function.
The support center introduced an automatic answering system.
留守番電話 is an answering machine, a physical device or service that records messages, while 自動応答 is the broader concept of automatic answering, often used in computing contexts.
Compound of 自動 (automatic) and 応答 (response, answer).