SMTP Error! Data not accepted.

I am developing a new site on a subdomain, and to test the cotact forms I used a domain email address for the from address (as in [email]info@domain.com[/email] sending from sub.domain.com).
The error message I get is:

SMTP Error! Data not accepted. SMTP server error: Message rejected: Email address is not verified.

Is this due to apparent conflict between the subdomain sender and the domain address, or could there be something else operating here?

Solved!

My host added a verification code to the DNS for the SMTP server. Now the data is accepted and the email goes.