Knowledge Is Power

Email Spoofing

E-mail spoofing is the forgery of an e-mail header so that the message appears to have originated from someone or somewhere other than the actual source. Distributors of spam often use spoofing in an attempt to get recipients to open, and possibly even respond to, their solicitations. Spoofing can be used legitimately. Classic examples of senders who might prefer to disguise the source of the e-mail include a sender reporting mistreatment by a spouse to a welfare agency or a "whistle-blower" who fears retaliation. However, spoofing anyone other than yourself is illegal in some jurisdictions.
E-mail spoofing is possible because Simple Mail Transfer Protocol (SMTP), the main protocol used in sending e-mail, does not include an authentication mechanism. Although an SMTP service extension (specified in IETF RFC 2554) allows an SMTP client to negotiate a security level with a mail server, this precaution is not often taken. If the precaution is not taken, anyone with the requisite knowledge can connect to the server and use it to send messages. To send spoofed e-mail, senders insert commands in headers that will alter message information. It is possible to send a message that appears to be from anyone, anywhere, saying whatever the sender wants it to say. Thus, someone could send spoofed e-mail that appears to be from you with a message that you didn't write.

Cc: stands for "carbon copy." Anyone listed in the Cc: field of a message receives a copy of that message when you send it. All other recipients of that message can see that the person you designated as a Cc: recipient received a copy of the message.
Bcc: stands for "blind carbon copy." This is similar to the Cc: feature, except that Bcc: recipients are invisible to all the other recipients of the message (including other Bcc: recipients). For example, if you send a message To: johndoe@yahoo.com and Bcc: janedoe@yahoo.com, then johndoe sees himself as the message's only recipient. Janedoe, on the other hand, is "in the know"—she can see that you sent the message To: johndoe, and that you blind-copied her. To add an entry in the Bcc: field, click the "Show BCC" link to the right of the "To:" field.