How do you ensure if the e-mail is authentic and sent from fedex.com?

A common technique for luring e-mail users into opening virus-launching attachments is to send
messages that would appear to be relevant or important to many of their potential recipients. One
way of accomplishing this feat is to make the virus-carrying messages appear to come from some
type of business entity retailing sites, UPS, FEDEX, CITIBANK or a major provider of a common
service.
Here is a fraudulent e-mail claiming to be from FedEx regarding a package that could not be
delivered. This mail asks the receiver to open an attachment in order to obtain the FEDEX tracking
number for picking up the package. The attachment contained in this type of e-mail activates a
virus.

Vendors send e-mails like this to their customers advising them not to open any files attached with
the mail, as they do not include attachments.
Fraudulent e-mail and legit e-mail that arrives in your inbox contain the fedex.com as the sender of
the mail.
How do you ensure if the e-mail is authentic and sent from fedex.com?

A.
Verify the digital signature attached with the mail,the fake mail will not have Digital ID at all

B.
Check the Sender ID against the National Spam Database (NSD)

C.
Fake mail will have spelling/grammatical errors

D.
Fake mail uses extensive images,animation and flash content