Safe= Yes | No
The list header keyword, "Safe=", controls the e-mail address LISTSERV places in the SMTP MAIL FROM: field, which is where well-behaved mailers will return delivery errors. With "Safe= No", these errors are sent to the list address as before, hopefully to be intercepted by the loop detector and passed on to the list owner. With "Safe= Yes", the error address is set to 'owner-listname', and delivery errors sent to that address are passed on to the list owner without the risk of creating a mailing loop. The default is "Safe= Yes".
IMPORTANT: The use of "Safe= Yes" does not guarantee that all errors will go to the 'owner-listname' mailbox. Unfortunately, there are many non-compliant mailers which will continue to send the error back to the list (usually because it is listed in the 'Reply-To:' or 'Sender:' field). Using "Safe= Yes" significantly decreases the potential for mailing loops, but not enough to actually code "Loopcheck= No", unless you are sure that all your subscribers have compliant mailers.