Bound the reply and repeat rate
05The reply has its own message headers, transport envelope and content. Limits reduce loops, amplification and unintended disclosure.
Chosen 7-day default: send the first away notice, suppress repeat notices at day1 and day6, reconsider at day7. Reconsidering is not an obligation to send.
Source for this drawing: RFC 3834 · Read RFC section 3.3 ↗
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.
Choose an outgoing MAIL FROM that makes loops unlikely. A null reverse-path <> MAY be used, or a dedicated address that will not automatically respond. This is separate from the non-null RCPT TO destination.
- Choose an outgoing MAIL FROM that makes loops unlikely. A null reverse-path <> MAY be used, or a dedicated address that will not automatically respond. This is separate from the non-null RCPT TO destination.
- NOTIFY=NEVER is RECOMMENDED on the response RCPT command when the server supports the SMTP DSN extension. It is not a command to use with a server lacking that extension.
- Personal and Group responses SHOULD be brief and text/plain. They SHOULD NOT quote significant incoming content or include incoming non-text parts or attachments; specialized content-transformation services have a scoped exception and MUST prevent abuse.
- For repeated away/busy notices, Personal and Group responders SHOULD NOT send the same reply to the same sender more than once in several days; 7 days is the RECOMMENDED default, not a mandatory timeout for every service. Automatically generated text SHOULD NOT reveal otherwise unavailable personal information.
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 ↗