
Ask HN: How do email services prevent auto-reply loops? - whack
Suppose persons A and B are both out-of-office, and have enabled their respective auto-reply feature. Person A then sends an email to person B.<p>In a naive email service, that initial email will trigger an auto-response from B, which will then trigger another auto-response from A, which will trigger another auto-response from B... and you wind up with an infinite loop.<p>I hear that most email services already have systems in place to detect and prevent the above loop from happening. How is this implemented?<p>By checking to see if the sender has already sent an identical email recently?<p>By checking to see if the message contains various hard-coded strings such as &quot;out of office&quot;?<p>By checking to see if the reply was sent almost immediately after the original message was sent?<p>All of the above heuristics seem like they could be broken under various scenarios. Are email services using some other more deterministic way to detect auto-reply emails?
======
deedubaya
Email servers will add a message header if an auto-responder shouldn't respond
to the message. A google search will provide more details.

