@misc{rfc3974,
    series =    {Request for Comments},
    number =    3974,
    howpublished =  {RFC 3974},
    publisher = {RFC Editor},
    doi =       {10.17487/RFC3974},
    url =       {https://www.rfc-editor.org/info/rfc3974},
    author =    {Motonori Nakamura and Jun-ichiro Itoh},
    title =     {{SMTP Operational Experience in Mixed IPv4/v6 Environments}},
    pagetotal = 10,
    year =      2005,
    month =     jan,
    abstract =  {This document discusses SMTP operational experiences in IPv4/v6 dual stack environments. As IPv6-capable SMTP servers are deployed, it has become apparent that certain configurations of MX records are necessary for stable dual-stack (IPv4 and IPv6) SMTP operation. This document clarifies the existing problems in the transition period between IPv4 SMTP and IPv6 SMTP. It also defines operational requirements for stable IPv4/v6 SMTP operation. This document does not define any new protocol. This memo provides information for the Internet community.},
}