What does the error Too many Received headers – suspected mail loop mean?
A0061: Whenever a message passes through an MTA, a Received: header gets added. Exim counts the number of these headers in incoming messages. If there are more than the value of received_headers_max (default 30), Exim assumes there is some kind of mail routing loop occurring. For example, host A passes the message to host B, which immediately passes it back to host A. Check the Received: headers and the mail logs to determine exactly what is going on. One common cause of this problem is users with accounts on both systems who set up each one to forward to the other, thinking that will cause copies of all messages to be delivered on both of them.
