Check Email Headers
Another good practice according to Kaspersky Lab's Tanase is to check the email headers to confirm the source of the email message. This isn't always foolproof because addresses and source information can be easily spoofed.
Email headers can give the details of a sender. Google and other services provide email header analysis tools that can determine the legitimacy of a sender's IP address. In addition to the IP address, the header will show the Mail Server used and the details of the sender's service provider. Phishers can spoof the email headers, but usually telltale signs can provide clues as to whether a message is legitimate. When in doubt, throw it out.