Stop replies that would feed a loop
02Receiving a message does not automatically justify sending one back. Check why a response would be useful before creating it.
A vacation responder checks explicit recipient fields and its configured abuse policy. The pictured no-recipient example is suppressed under the recommendation, not a claim that all Bcc mail is invalid.
Source for this drawing: RFC 3834 · Read RFC section 2 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
An automatic responder MUST NOT blindly respond to every message. Messages with Auto-Submitted values other than no SHOULD NOT receive an automatic response; this is a recommendation, not a universal MUST NOT.
- An automatic responder MUST NOT blindly respond to every message. Messages with Auto-Submitted values other than no SHOULD NOT receive an automatic response; this is a recommendation, not a universal MUST NOT.
- A responder MUST NOT generate a response whose destination is the null address <>. This is the destination of the proposed reply, not a ban on every message received with an empty envelope sender.
- Personal or Group vacation notices SHOULD NOT be issued unless the recipient is explicitly listed in a recipient field. This heuristic can suppress legitimate hidden-Bcc mail. Trusted-correspondent restrictions and ignoring List-* or suspicious content are optional policies; missing automation headers do not prove human authorship.
Fictional example.org addresses. Independent examples are labelled; this is guidance for responders, not a full mail parser or an authentication mechanism.
Read the RFC section ↗