%% You should probably cite draft-ietf-lamps-rfc5751-bis instead of this I-D.
@techreport{schaad-rfc5751-bis-01,
    number =    {draft-schaad-rfc5751-bis-01},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-schaad-rfc5751-bis/01/},
    author =    {Jim Schaad and Blake C. Ramsdell and Sean Turner},
    title =     {{Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.5 Message Specification }},
    pagetotal = 49,
    year =      2016,
    month =     jul,
    day =       8,
    abstract =  {This document defines Secure/Multipurpose Internet Mail Extensions (S/MIME) version 3.5. S/MIME provides a consistent way to send and receive secure MIME data. Digital signatures provide authentication, message integrity, and non-repudiation with proof of origin. Encryption provides data confidentiality. Compression can be used to reduce data size. This document obsoletes RFC 5751.},
}