DNN will only send from the designated site administrator so you can do what a few people do - have two or sometimes three administrator accounts.  The one you want email to be sent through is then assigned the *site administrator* from the Admin/Settings / and look down the page for the *site admistrator* dropdown box.

It automatically reads who the site adminitrators are - based on you having added their name to be an administrator, and you can then use the one with the email address you want to use.

But what you want to do is an automated procedure within DNN so at this stage, if you're the administrator on the site with an email address you don't want to use, you would need to change or add another administrator and assign that in the settings.  You can't pick and choose who you want to have the email address sent from.

I read over this once or twice - hope it's not too difficult to understand.   

Nina Meiers