%% You should probably cite draft-ietf-appsawg-nullmx instead of this I-D.
@techreport{delany-nullmx-00,
    number =    {draft-delany-nullmx-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-delany-nullmx/00/},
    author =    {Mark Delany},
    title =     {{A NULL MX Resource Record means "I never accept email"}},
    pagetotal = 5,
    year =      2005,
    month =     apr,
    day =       6,
    abstract =  {A common strategy of SMTP servers when deciding whether to accept an email or not, is to ensure that the 2821.MailFrom contains a domain willing to accept non-delivery email (aka bounces). When the 2821.MailFrom domain has a DNS MX Resource Record (RR), it is making an explicit statement that it is willing to accept email. However, when the domain has just a DNS A (or AAAA) RR, there is no such clarity as most hosts on the Internet advertise an A RR regardless of whether they want to accept email or not. The NULL MX RR formalizes the existing mechanism by which a domain communicates that it will never accept email.},
}