[1] Naik D. C , INTERNET standardy a protokoly. První vydání. Computer Press, Praha, 1999, ISBN 80-7226-146-0

[2] Postel J. B.,
      RFC 821 Simple Mail Transfer Protocol, ftp://ftp.isi.edu/in-notes/rfc821.txt

[3] Partridge C.,
      RFC 974 MAIL ROUTING AND THE DOMAIN SYSTEM , ftp://ftp.isi.edu/in-notes/rfc974.txt

[4] RFC 1321 - kódovací algoritmus MD5

[5] Crocker D. H.,
      RFC 822 Standard for the Format of ARPA Internet Text Messages, ftp://ftp.isi.edu/in-notes/rfc822.txt