1. mailman can send message to sendmail 2.but sendmail can't send the message to mail list The original message was received at Thu, 14 Oct 2010 09:41:53 +0700 from apache at localhost ----- The following addresses had permanent fatal errors ----- somt at cbs.pea.co.th (reason: 550 5.1.1 <somt at cbs.pea.co.th>... User unknown) (expanded from: somt at cbs.pea.co.th) ----- Transcript of session follows ----- ... while talking to [127.0.0.1]: >>> DATA <<< 550 5.1.1 <somt at cbs.pea.co.th>... User unknown 550 5.1.1 somt at cbs.pea.co.th... User unknown <<< 503 5.0.0 Need RCPT (recipient) thanks for help