asterisk users - Aug 2005 - Fax to email using mime-contruct

I have followed and succesfully receive incoming faxes to email with
Scott Laird's faxing with asterisk guide.
http://scottstuff.net/blog/articles/2004/03/28/faxing-with-asterisk

But, I'm receiving the email from root@mydomain.com.
I would prefer it to receive from asteriskfax@mydomain.com.
How do I achive this? Please advice. I'm using postfix.

Thanks.