1. A method comprising the steps of: (A) receiving an email message from a simple mail transfer protocol (SMTP) server, the email message comprising: (A1) a 32-bit string indicative of the length of the email message; (A2) a text body; (A3) an SMTP email address; (A4) a domain name corresponding to the SMTP email address; (A5) an attachment; (B) tokenizing the text body to generate tokens representative of words in the text; (C) tokenizing the SMTP email address to generate a token representative of the SMTP email address; (D) tokenizing the domain name to generate a token that is representative domain name; (E) tokenizing the attachment to generate a token that is representative of the attachment, the tokenizing step comprising the steps of: (E1) generating a 128-bit MD5 hash of the attachment; (E2) appending the 32-bit string to the generated MD5 hash to produce a 160-bit number; and (E3) UUencoding the 160-bit number to generate the token representative of the attachment; (F) determining a probability value for each of the generated tokens; (G) selecting a predefined number of interesting tokens, the interesting tokens being the generated tokens having the greatest non-neutral probability values; (H) performing a Bayesian analysis on the selected interesting tokens to generate a spam probability; and (I) categorizing the email message as a function of the generated spam probability.