ezmlm lists (ezmlm-idx>=0.31) remove ‘Received:’ headers from incoming messages by default. This can be prevented with the ezmlm-send(1) -r switch. When the headers are propagated, especially sublist message may have many (15-20 or more), ‘Received:’ headers. If there is a poorly configured sendmail host with a “hopcount” set too low, it will bounce these messages, incorrectly believing that the many ‘Received:’ headers are due to a mail loop. The reason that administrative from the list do not bounce is that they have fewer ‘Received:’ headers, since they originate from the sublist.
The message with all headers including the removed ‘Received:’ headers can be retrieved from the list archive with the ‘-getv’ command. The top incoming ‘Received:’ header is added by qmail at the receipt to the list (or last sublist) host. This header is not removed, to allow the recipient to determine when the message reached the list.