%% You should probably cite draft-ietf-spfbis-4408bis instead of this I-D.
@techreport{kitterman-4408bis-00,
    number =    {draft-kitterman-4408bis-00},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-kitterman-4408bis/00/},
    author =    {Scott Kitterman and Wayne Schlitt},
    title =     {{Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1}},
    pagetotal = 55,
    year =      2011,
    month =     oct,
    day =       24,
    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 Sender 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.},
}