There is a RFC 3834 dedicated for automated email responses.
In short, it recommends:
Send auto-responses only to address contained in the
Return-Pathheader of an incoming message, if it is valid email address. Particularly “<>” (null address) in the
Return-Pathof the message means that auto-responses must not be sent for this message.
When sending auto-response, MAIL FROM smtp command must contain “<>” (null address). This would lead to Return-Path:<> when message will be delivered.
Use Auto-Submitted header with value other than “no” to explicitly indicate automated response.
One note: it is not worth to explicitly set Return-Path header in outgoing message, as this header must be rewritten by envelop address (from MAIL FROM smtp command) during delivery.