How to send mail from zimbra command line

I am vikas. i am looking a command that can send mail from zimbra mail-store server to external world. but as i checked in zimbra not getting Any program that have role of sending mails. that is why i am relay email through Zimbra MTA server. now i am going to use below command but still getting variable error.

awk 'BEGIN{print "Subject:test mail!\nFrom:Mailadmin <admin@knowledgelinux.com>"}{printf("%s\015\n", $0)}' $message file-name=/test.txt | sendmail -t "mail@knowledgelinux.com"

awk: command not found