PO no output when i delete all items with error ME140

Hello Experts, we are using the PO message type NEU to send email to vendors for notification, and if I only marked some of the items to deletion flag , the email works correct ,and will have an new PO output send to vendors, but if I delete all the items , the PO message will be stopped by the error . when I go to the message tab, I can see there is an error mentioned ME 140 No print-relevant changes to document XXXXXXXXX exist. could someone help to advise me if there is any configuration I need to change ? thanks