If you want to control the NOTIFICATION or REPLYTO address you can do this in the required page's OPTIONS tab.
We used to do it this way but due to changes in GMAIL and other ISPs and email clients, we have had to stop doing this. If an incoming email server knew we were not authorised to send emails on behalf of the customer, then many of those emails got marked as spam. It's a no win situation, because either the email is marked as spam, or the email's are difficult to sort or reply to.
All emails that originate from our server now use the PRIMARY CONTACT EMAIL of the website, as of October 2014.
Historically we used to use the customers email address, but those emails have a tendency to go to your spam folder, because we are not authorised to send emails on behalf of other people. Our system has to use the FROM address that we are entitled to use. And we put the customers email into the suplementary REPLYTO address field. Different email clients will treat this approach differently, some will display the FROM address and others will display the REPLYTO address, however, when you click REPLY, you should get the REPLYTO address.
But in GMAIL, this is not alway so. If your FROM address is the same as the current INBOX, and you click REPLY, you won't get the result you want, and you will need to find a way to work around it. And/or copy/paste the email address from the body of the email.
There are many different possibilities for this
You can set validation, and more via the OPTIONS tab - then the links show in the tool tips.