Use this step by step instructions to find out who or what device logged in or used your Gmail account or Google business account. test
This is an important security verification every Gmail or Google Business email account holder should do routinely.
Checking the details
STEP 1:
Log-in to your Gmail account or Google Business email.
STEP 2:
Scroll all the way down until you can see the footer of the Gmail screen. Then click on “Details” on the bottom right corner, in small writing.
STEP 3:
A new window will pop-up that says “Activity on this account”.
Who used or logged into Gmail account?
You cannot know exactly who, however, you can know the IP address of the user. The IP address can tell you if it was from one of your computers or even your phone. If it is not yours, then you should be concerned.
Look at the screenshot “Activity on this account” and notice how it provides three columns. Access Type, Location IP, and Date/Time.
Access Type
The first column on the left says Access Type (browser, mobile, POP3, etc.) This column tells us if the account was used through an application, a browser, or other.
Looking at each activity, you can click “Show details” to learn more about the user. If you show details under “Authorized Application”, it may show you the name of a mobile phone such as iPhone. 
Location (IP address)
The second column is called “Location (IP address)”. This column provides the IP address and approximation of where the user is located. 
I have inked my IP address to protect it from public, but this IP address can in fact tell you where the user is at. Most of the time, the IP address will be yours since you are likely the main user. So how do you know what is your IP address? Simple, scroll down in the “Activity on this account” window and at the bottom in small writing you will see this sentence “This computer is using IP address ##.##.###.##. You can see it in the first screen shot in this instruction “Activity on this account”.
If your computer IP address does not match any of the IP addresses, then you need to ask yourself if you access your Gmail or Google business email with another computer or device such as a mobile phone.
A mobile phone will also have its own IP address. You can check your phone’s IP address by using a Google web browser on your smartphone and searching “what’s my IP address”. The results will first yield your IP address. Now check if it is the same as the IP address on the “Activity on this account” window.
If you use another computer, check the IP address the same way described for mobile phone. Simply open a Google browser and search “what is my IP address”. Google will provide it at the very top of the results. 
Date/Time
To the right will be a column called “Date/Time”. These entries will be displayed in your time zone. They are shown for each Access.
Summary
Checking the users of your Gmail or Google business email account is important to make sure that nobody who should not have access is not seeing your emails.
If you find an IP address in your Activity that is not from a device you know, then it is important that you contact your email provider who could be an IT administrator. They will be able to unregister the IP and change your password to stop the intruder.
If you have employees or friends who are not aware of this, please forward this Check Gmail Account Activity instructions to them.
