Some people wonder when they have an email autoresponder, and
the person who sends a message to them also has an email autoresponder,
this will cause a sort of loop between the two email autoresponders.
Fortunately, such a loop is very unlikely to occur. Autoresponders save the email address to which they have already sent an automatic response and will match it with new incoming messages. If the new message comes from a mail in the list and the system has not sent a message to it in the last 1 hour, no automatic response will be sent.
In other words, a single email address can receive an autoresponse only once per hour.