I am new about zimbra, i setup successfully my server. send email is also working fine . Now i want to use send emails function form my other linux machine as client . my client machine connect with server and send email... i try but i got this error any help please....

root@quwic-s08 ~]# service sendmail restart
Shutting down sm-client: [ OK ]
Shutting down sendmail: [FAILED]
Starting sendmail: 554 5.0.0 No local mailer defined
554 5.0.0 QueueDirectory (Q) option must be set
Starting sm-client: [ OK ]