%% You should probably cite rfc6531 instead of this I-D.
@techreport{ietf-eai-rfc5336bis-16,
    number =    {draft-ietf-eai-rfc5336bis-16},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-eai-rfc5336bis/16/},
    author =    {Wei MAO and Jiankang Yao},
    title =     {{SMTP Extension for Internationalized Email}},
    pagetotal = 18,
    year =      2011,
    month =     nov,
    day =       9,
    abstract =  {This document specifies an SMTP extension for transport and delivery of email messages with internationalized email addresses or header information. {[}STANDARDS-TRACK{]}},
}