Hi,
Best practice to always use existing addresses and to make sure your FROM, REPLY and BOUNCE addresses have an addrresss that matches the domain of your website. As long as the have the same domain part they can differ in the local part.
This way DMARC will align with your DKIM and SPF. If needed you can use a different domain for the REPLY address, but it looks way more professional if it matches your website domain.
In case you activate the automatic bounce handling that comes with the Enterprise version it's recommended to use a dedicated bouce email account (like bounce@yourdomain.com or similar).
