A term that refers to standards, such as Sender ID, SPF and DomainKeys/DKIM, that serve to identify that an email is really sent from the domain name and individual listed as the sender. Authentication standards are used to fight spam and spoofing.

Building an Opt-In List, Building Relationships
If you aim for success, you must do everything within your means to achieve that. You just donÃt go on sitting there in your house complaining about not getting as much profit as you expect.