We are running ListServ on Solaris machine. Yesterdy when a user (who is an editor) posted a reply on a 'send=editor, hold' list, the post was forwarded to the first editor with the following message: The enclosed message, found in the XXX mailbox and shown under the spool ID 31925 in the system log, has been identified as a possible delivery error notice for the following reason: "Sender:", "From:" or "Reply-To:" field pointing to the list has been found in mail body. the sender used the same email address to XXX list many times before without problems. All the other members replied to other's post (including 'To: [log in to unmask]) too. Would any one please shed light on this message? Thanks! Shinn