how to check whether E-mail Account was hacked ?

Here is a step by step guide:

Step 1: Open the ˜Last Account Activity’ Section Your Inbox..

you will find it At the bottom of your Gmail inbox there is a ˜Last Account Activity’ section.

Click on  "details" ......

Step 2: watch your Account access activity recently

 you will see :

• Accessed type
• The IP address 
• times of access

 

Step 3: Understand the IP addresses – Has your Gmail really been hacked?

 

for your own investigation, you can use DomainTools like website tools to identify the IP address. This will help you differentiate normal activity and hacked.

Step 4: Understand the Google alerts –  suspicious activity

 

Google also monitors, and alerts you if it sees suspicious activity both in your inbox, as well as your recent activity log.  When this happens, and the IP addresses look suspicious, it is advisable to play it safe, assume your Gmail account has been hacked, and change your passwords immediately.

Step 5: Sign Out All Other Sessions – If you forgot to sign out on a public computer

1. It won’t fix any hacked Gmail accounts, but it will resolve any careless mistakes.

2. This method is also fruitfull if you have lost your mobile phone or you forgot to        logout from anywhere. 

Step 6: What to do if your Gmail account has really been hacked

The first thing you do is change both your password and security question right away.

• Choose a question only you know the answer to – make sure the question isn’t associated with your password.
• Make sure your answer is memorable, but not easy to guess.  (for example, avoid your mother’s maiden name, your birth date, your first or last name, your social security number, your phone number, your pet’s name, etc.). 
• Use an answer that is a complete sentence for even more security.