Isn't it possible for a domain administrator to access the SOAP admin APIs?

Following KevinH's examples, I am able to do delete accounts via a perl script with the the Zimbra admin's credentials but, when I change the creds in the script to those of a domain adminstrator, I get a big fat AUTH_FAILED stack trace.

Shouldn't this be possible?

Btw, - I'm trying to use the script to delete an account in the domain adminstrator's domain. That is the domain administrator can delete the account using the web interface.