Hi, Derek: Because of the demands of electronic discovery, there are actually a large number of software packages designed to sort through email, search it, and provide for (usually *very*) basic tagging. Many of these are run as services, often with heavy support, and with the heavy fees large law firms can afford. So, the problem isn't so much finding software that can handle large numbers (tens of millions) of emails, but rather finding software that can do what you want it to. Searching the literature for electronic discovery will likely yield legal--rather than technical--articles. However most texts on computer and network forensics now discuss handling large collections of email. On the legal side, there is searching and query systems (like http://www.metalincs.com/), and on the forensics side, there are tools that do much the same thing, but with different ends. These may provide a start: http://portal.acm.org/citation.cfm?id=1113074 http://portal.acm.org/citation.cfm?id=1065226.1065291 - Alex -- // // This email is // [X] assumed public and may be blogged / forwarded. // [ ] assumed to be private, please ask before redistributing. // // Alexander C. Halavais, cyberflâneur // http://alex.halavais.net //