"He is using Gmail as a backend to his own mail setup"

No, he is using a normal forward for those who want to receive their mail at gmail. He is not using gmail as his backend. You should read the original article.

I did read the article and that's exactly what he's doing. He forwards everything to Gmail, and then allows users to send from Gmail via his SMTP server (or maybe doing some spoofing but it wouldn't look so clean). Essentially outsourcing hosting of inboxes (but just inboxes) to Gmail.

I run my own mail server, but most of my employees use Gmail. So I have forwarding set up: [email protected] simply forwards to [email protected]. When sending mail using their Gmail account, they set their From line to [email protected]. (Google lets you do this if you jump through some hoops to verify that you can actually receive mail at that account.)

And that is the description for a fairly normal "forward all my mail to my personal inbox" scenario. Its not rocket science and it is not using gmail as his backend. We do it with part-time faculty.

You are misunderstanding what is happening. He is not using Gmail, his employees are.

Those are Gmail accounts belonging to his employees but he is using them in the back of his mail setup instead of hosting @dnalounge.com inboxes himself (or paying Google to).

He doesn't use them. His employees chose to forward their email because they want to use the same interface for both their work and personal email. He does host @dnalounge.com inboxes.