@misc{rfc4408,
    series =    {Request for Comments},
    number =    4408,
    howpublished =  {RFC 4408},
    publisher = {RFC Editor},
    doi =       {10.17487/RFC4408},
    url =       {https://www.rfc-editor.org/info/rfc4408},
    author =    {Wayne Schlitt and Meng Weng Wong},
    title =     {{Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1}},
    pagetotal = 48,
    year =      2006,
    month =     apr,
    abstract =  {E-mail on the Internet can be forged in a number of ways. In particular, existing protocols place no restriction on what a sending host can use as the reverse-path of a message or the domain given on the SMTP HELO/EHLO commands. This document describes version 1 of the ender Policy Framework (SPF) protocol, whereby a domain may explicitly authorize the hosts that are allowed to use its domain name, and a receiving host may check such authorization. This memo defines an Experimental Protocol for the Internet community.},
}