[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