The problem of document browsing and navigation attracts the attention of researchers in information retrieval and also in human-computer interface design. Similarly, in conceptual structures research, the use of the concept lattice as an information space for the navigation of documents was one of the pioneering applications of Formal Concept Analysis and maintains the interest of many researchers in the field due to its practicality. MailSleuth is the extension of previous research work and a number of

practical projects preceded it; namely, CEM [Cole and Eklund, 1999, Cole et al., 2000, Cole and Stumme, 2000, Eklund, 2002, Cole et al., 2003] and Rental-FCA [Cole and Eklund, 2001]. Other related and concurrent efforts that are similarly motivated include [Koester, 2006]. MailSleuth distinguishes itself from these in that the software has been extensively tested for usability. MailSleuth has provided a platform for enhancing the practicability of browsing and navigating information spaces using concept lattices, particularly testing the suitability of the metaphor for non-FCA trained users.