(SPF)
Stands for Sender Policy Framework and it is an open standard for a technical method developed to prevent forgery of sender e-mail address. The current version of SPF is called SPF Classic which protects the envelope sender address used for the delivery of messages. See the box on the right for a quick explanation of the different types of sender addresses in e-mails.More precisely, SPF Classic allows to be specified the mail sending policy for each domain or with other words, which mail servers will be used to send mails from a particular domain.

