What is E-mail Spoofing?

Email spoofing as the name goes is nothing but imitation of a email id. So the mail that has a from address of xyz@domainname.com may not actually be send by a person with the existing email id. This is easily done if one change the from address. Basically in this scenario, 1000's of emails are send from a client machine with the user not knowing about it OR user imitating another email id (spoofing)

Most e-mail providers will require authentication (a user name and a password) in order to connect to the e-mail server and send an e-mail. This may cut down on e-mail spoofing but does not entirely prevent it.

Eg.: If a user has a email user is using a email desktop client, and has malware on the client machine. Spoofing mails as spam mails can orignate from such machine. Its the machine sending the email and not the email user. The local network engineer should immediately remove the machine from the network and clean the machine to make sure if not infected with any malware of spyware that's leading to spam mail and is more like email spoofing.

Many times when spoofing email as spam mails originates, this can even risk a server IP and if complained then server IP can be listed on various RBL as spam server and hosting companies can loose business just because of the negligence of the client and unsecured machine.

Many professional hosting companies suspend the account if it traces spoofing that can be due to malware or even intentional. whatever maybe the reason the server of the hosting company is at a higher risk of getting listed on RBL's