[Zope] MailHost problem

hi i got this error on my mailhost script which is built in on zope i got this following error Zope Error Zope has encountered an error while publishing this resource. Error Type: SMTPSenderRefused Error Value: (550, '5.0.0 Access denied', 'email@localdomain.com) im using sendmail as MTA do i need to configure anything else? i can send email on the command line my sendmail works but this problem occur