My answer: Use gmail's "last account activity" function to see information on utilization of your account.
It is explained here: https://support.google.com/mail/answer/45938?hl=en
Here is an excerpt:
You can see the last 10 IP addresses and approximate locations that
accessed your Gmail account.
If you got a warning about suspicious activity in your account, you
might also see up to 3 additional IP addresses that have been labeled
There are a few reasons you may see multiple IP addresses or locations
in your activity:
If you use POP or IMAP to read your mail on other services, like Apple
Mail or Microsoft Outlook, this location information will be included,
If you use Mail Fetcher, a Google IP will show up because your
messages are being fetched through a Google server.
If you use Gmail on a phone or tablet, your Internet service or mobile
carrier's location may show up. This may be a location far from where
you are. As long as the name of the carrier matches yours, this isn't
While on this topic, it is highly suggested you use 2FA security on gmail to prevent this from happening. I use Google Authenticator on my Android phone so I can click Yes or No to any unknown logins.