1. A method to determine a probability that an email message is spam, the method comprising: (a) receiving an email message; (b) identifying one or more words and/or phrases of the email message that are likely being obfuscated; (c) identifying one or more obfuscation techniques that are being used to obfuscate the one or more words and/or phrases that are identified as likely being obfuscated; and (d) determining a probability that the email message is spam in dependence on at least both of the following which particular one or more words and/or phrases are identified as likely being obfuscated, wherein identifying some particular words and/or phrases as likely being obfuscated increases the probability that the email message is spam more than identifying other particular words and/or phrases as likely being obfuscated, and which particular one or more obfuscation techniques are identified as being used to obfuscate the one or more words and/or phrases that are identified as likely being obfuscated, wherein identifying use of some obfuscation techniques increases the probability that the email message is spam more than identifying use of other obfuscation techniques; wherein one or more of steps (b), (c) and (d) are performed using one or more processors.