9. The system of claim 8 , wherein the instructions to determine a probability that the email message is spam also include instructions to determine the probability that the email message is spam also in dependence on a quantity of words and/or phrases identified as likely being obfuscated, wherein the higher the quantity of words and/or phrases of the email message identified as likely being obfuscated the higher the probability that the email message is spam.
8. A system to determine a probability that an email message is spam, the system comprising: one or more processors; machine-readable storage medium including instructions that are executable by the one or more processors; wherein the instructions include instructions to receive an email message; instructions to identify one or more words and/or phrases of the email message that are likely being obfuscated; and instructions to identify 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 instructions to determine 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 being used to obfuscate the one or more words and/or phrases that are identified as likely being obfuscated, wherein detecting use of some obfuscation techniques increases the probability that the email message is spam more than detecting use of other obfuscation techniques.