All of the Web Hosting servers are setup to take advantage of the GT Outbound service. No additional configuration is needed on the Web Hosting servers in order for your website to send email from those servers. You should configure your content management system (i.e. Drupal) as described in the setup documentation for that application.
Understanding "From" Addresses from "Envelope-Senders"
The "From" address is an email address that you can control through your application or custom php code. It's what your recipient will see, and it will be your default Reply-To, if you do not also specific that.
The "Envelope-Sender" of your message will be your <site_user>@<sitename> (i.e. If my site user is "admin" and my site name is "s1.test.gatech.edu", then my envelope-sender will be firstname.lastname@example.org).
Caution: If your Site Name is also a valid GT email domain (i.e. if my site name is "oit.gatech.edu" and the email domain "oit.gatech.edu exists on the GT mail routing infrastructure), then your envelope-sender must be a valid email address with a valid destination (i.e. not disabled). If you have any questions on whether your site name is also an email domain or if you need assistance setting up this email address, please contact the OIT Technology Support Center or your Department CSR.