Inside the seven categories of dumb things people write in business e-mail: freaked out, angry, conspiratorial, confessional, friendly advice, personal and confused.A couple of weeks ago\u00a0I wrote about my worries, and my last worry was what malware might be lurking in our e-mail archives.To recap: When I recently tested a new e-mail indexing tool, it opened messages and their attachments that I had filed away unopened or deleted but not purged. In the process, the indexer turned up a treasure trove of viruses and worms that for one reason or another my anti-virus system had not caught.This led me to worry about the scale of this problem in the business world - these stock piles not only act as a pool of latent infection that periodically will be disturbed, cause problems and cost money, but their existence means that malware never will be eradicated completely. A big worry indeed. Well, I just heard of a bigger liability that lurks in your messaging systems: old message content.I chaired a couple of sessions last week at the Inbox conference in San Jose, and one of the other sessions I attended was titled "The Email Comedy Club: Membership Details." The speakers were Joan Feldman, president of Computer Forensics, and Elizabeth Charnock, CEO of\u00a0Cataphora.These companies specialize in electronic discovery - the art and science of analyzing corporate data and e-mail for legal cases. What struck me first was the scale of the work they get involved in, compiling and processing terabytes of data and building up a picture of what was said, by whom, how it was said, what was not said and when these events happened.But wow! The dumb things people put in e-mail. Charnock groups the dumb messages into categories, what she calls the "The Seven Ugly Dwarves": freaked out, angry, conspiratorial, confessional, friendly advice, personal and confused.A few of Charnock's examples are worth citing, such as this freaked out message: "It is all hopeless. It can't be done. We have to let the client know we can't deliver on this contract. There are too many risks of defects." Charnock points out that this could be a tired, frustrated employee letting off steam, or it might be a whistle-blower indicating a real problem.Or how about implied conspiratorial exchanges: 10:23 a.m., Joe to Jane: "The stock will be going up by at least 20% tomorrow. Don't tell anyone." Followed by 10:39 a.m., Jane to Jill: "Meet me in the cafeteria in 10 minutes."Friendly advice can be revealing: "If the auditors find real problems, there could even be a criminal issue. This is very serious stuff. You really need to look into this yourself." As Charnock pointed out, this helpful friend just removed the excuse of ignorance.Then there are the personal messages: "I had the most amazing LSD trip last night. It changed my life. I want to tell you all about it." Charnock says that this was the beginning of a real sequence of messages that, as you might imagine, would not be the sort of thing you'd want floating around your messaging archives waiting to become part of a discovery process.The thing that Charnock and Feldman vigorously promoted was the need for corporate policies on acceptable e-mail use and e-mail retention. In a subsequent discussion it became apparent that the majority of companies they deal with either fail to create such policies or, if they do, fail to make them work.An acceptable-use policy is crucial because people simply don't write carefully. As Charnock pointed out, e-mail is a significant risk as it is intimate, diary-like, often dashed off quickly, informal, heavily context-dependent stream of consciousness and has become a de facto means of business communication. It is also self-propagating, and there's a false presumption of safety in volume.Next week we'll discuss corporate e-mail AUPs and retention policies. In the meantime, how have you addressed these issues? 'Fess up to email@example.com.