Harri, Sorry if I wasn't clear, but I was speaking about problems with RFC822 mail sent to LISTSERV for command execution, not to a list. When the origin is unclear, you can omit the 'From:' field since 'Sender:' is always present. The only problem is where to send the ack messages, but that's something else. But when you're supposed to execute the thing as a command, it's different, you must be much more rigid, especially with mail origin validation. The previous versions used the RSCS origin but it seems to create mailing loops in some cases. By the way, if your LISTSERV tells you that your MAILER has been locked out, it's normal, it's a missing test in LSVMAIL that can cause a loop between your MAILER and LISTSERV when the mail origin could not be parsed. You don't have to SERVE the MAILER back, it doesn't need to send COMMANDS to LISTSERV itself (I mean commands From: Network Mailer <MAILER@localnode>). The problem with LISTSERV locking itself out is different and I'll have a look at it. Eric