Q: Do I need administrator status to remove size limit of my iMac OS X email server?

I am trying to remove the size limit of my iMac OS X email server. Below as the information that I copied from Terminal:

Last login: Thu Apr  9 17:24:47 on ttys000

192:~ grant$ sudo serveradmin settings mail:postfix:message_size_limit_enabled = no

WARNING: Improper use of the sudo command could lead to data loss

or the deletion of important system files. Please double-check your

typing when using sudo. Type "man sudo" for more information.

To proceed, enter your password, or type Ctrl-C to abort.

Password:

sudo: serveradmin: command not found

192:~ grant$

I don't know how to deal with this. Please help