@misc{rfc1846,
    series =    {Request for Comments},
    number =    1846,
    howpublished =  {RFC 1846},
    publisher = {RFC Editor},
    doi =       {10.17487/RFC1846},
    url =       {https://www.rfc-editor.org/info/rfc1846},
    author =    {Francis Dupont and Alain Durand},
    title =     {{SMTP 521 Reply Code}},
    pagetotal = 4,
    year =      1995,
    month =     sep,
    abstract =  {This memo defines a new SMTP ({[}1{]}) reply code, 521, which one may use to indicate that an Internet host does not accept incoming mail.},
}