I bought a friend's flight to Denver today and sent the confirmation from my new Gmail account.
The trip was scheduled for November 19. I told him I would forward the itinerary when it arrived. Most of the email was the way friends talked to each other in 2005, but I also gave him a direct recommendation: start using Gmail.
Gmail was still invitation-only. I had used one of my invitations for him and pointed out the amount of storage that came with the account. At the time, having enough space to keep mail instead of deleting it was a real change. I was already using the new address for travel confirmations, equipment purchases, job material, and messages that would previously have been spread across other accounts.
I was also testing the account against my SimAuthor address. Several messages from the first half of October have subjects like "test" and "test again." One asks the recipient to look at the header. Another goes to a separate testing address at the company. The bodies are only a few words because the message path and headers were what I was checking.
I was working as SimAuthor's network administrator in Boulder. The company had Windows, Linux, engineering labs, production services, and its own mail and network systems. Sending a message from Gmail to the company address was a quick way to see how an outside service reached the internal environment.
There is not enough in the surviving messages to say what exact mail setting I was diagnosing. The archive does show the transition clearly. Gmail was becoming my personal address while the SimAuthor account remained tied to work. I was using both, checking delivery, and asking other people to move over too.
The flight confirmation arrived after the purchase. I forwarded it and went back to the email tests.