Trying to get outbound SMTP working on a fresh Odoo 12 setup on Ubuntu 18.04 LTS.

Go to Settings > General Settings > Outgoing Mail Servers > SMTP

Setup server information.

Run Test Connection.

(had to manually modify test template because it was saying noreply@odoo.com rather than our domain when tried this earlier, with same error)

Get the following error message:

The server refused the test recipient (noreply@rpg.llc) with error b'5.7.1 <hawke@rpg.llc>: Sender address rejected: not owned by user odoo@rpg.llc'

Any ideas where I could be looking to figure out what I'm doing wrong?

Thanks!