I bought a friend's flight to Denver and told him the itinerary would show up in a minute.
Then I told him to get on Gmail.
Gmail still needed an invitation. I had used one of mine for him. The big sell was simple: more than two gigabytes of storage and no need to keep deleting mail. I had only been using the account for a short time, but travel confirmations, hardware purchases, job material, and normal personal mail were already landing there.
The flight was for November 19. The old message has the usual confirmation details, but those are private and not useful now. The useful part is that the new address was already doing real work. It was not a spare account I opened and forgot.
I was also sending test messages between Gmail and my SimAuthor address. The subjects were things like test and test again. One message asked somebody to check the header. Another went to a second company address. The bodies were a few words because the route and the headers were the point.
I ran the network at SimAuthor in Boulder. We had Windows and Linux systems, engineering labs, production services, firewalls, remote access, and our own mail setup. An outside Gmail account gave me an easy place to test what happened when mail crossed the edge of the company network.
I did not write down the exact mail problem in these messages. It could have been routing, filtering, forwarding, DNS, or a client setting. I know the tests reached both sides because the replies came back.
The itinerary arrived. I forwarded it. Gmail worked. Back to the next test.