I can't get this to work

Commands for Subscribing and Unsubscribing???

To subscribe to the list:

 TO: imailsrv@domain.com

 Subject:

 Body: Subscribe list_name

When I tried to subscribe myself into the list, I got the following message.

Subject: Help Message for (list_name) Rejected!

Body: The Help Message for (list_name) is for subscribers only!

Anyone has any idea what I did worng??? 

Does it make a difference if you add your name to the end

subject:  subscribe (list name) (your name)