This is a simple autoresponder for qmail. Mail is sent to help@my-company.com. An automatically generated response is sent back to the user with an address of "help@my-company.com". You can set the envelope sender to an empty string. However, some programs will parse the message for the "From:" field and send an autoresponse back to it. It is received at your autoresponder, and you now have a mail loop. This autoresponder also catches some other simple situations such as mail from a mailer-daemon, empty envelope sender, bulk precedence headers, etc.