The email that arrives in you inbox looks very official. It carries the familiar Yahoo! Mail logo and has a heading that warns, "Your Account Will Be Blocked."

If you're one of the millions of people who have a Yahoo! Mail account, you might be inclined to take the message seriously.

"Due to the congestion in all Yahoo! users accounts, Yahoo! would be shutting down all unused accounts," the message warns. "In order to avoid the deactivation of your account, you will have to confirm your e-mail by filling out your Login info below."

The message then asks for the user name, password, date of birth and country of residence. The request for such sensitive information, along with the not-quite-right grammar, is a tip off the very real-looking document is a fake.

"You should assume that any unsolicited message asking for your Yahoo! ID and password, security key, or other sensitive information is part of a scam to gain unauthorized access to your account," Yahoo! security told in an email.

If you have already entered your information into a suspicious message, Yahoo! Security advises users to immediately change their password and update any other information you provided.

If you find that you are no longer able to access your Yahoo! Mail account, contact Yahoo! Security and select the link "I gave my password to someone and am now unable to access my account."

If scammers gain access to your mail account, they also gain access to sensitive emails that you may be keeping. By hijacking your account, they can also use it to send out millions of spam email messages.