Google Responds to CNC Login

[Hotdog]

For the past couple of months Google sends an E-Mail every time I login to FutureQuest CNC. The message is, "We noticed a new sign-in to your Google Account on a Linux device. If this was you, you don’t need to do anything. If not, we’ll help you secure your account." It is addressed to postmaster@my website.

It is followed by a second E-Mail from Google which reads, "Hi my name,
Thanks for signing into Google on your Linux device.
Please confirm your Google Account settings are still right for you."

My only account relating to Google is on YouTube where I posted two videos over a year ago. My user name there is postmaster@my website. How and why does Google know when I log onto FutureQuest CNC?