This presentation, the third of six parts on the practical analysis of significant properties of digital objects, leads participants through an initial practical exercise to determine the properties of particular type of digital object, an email message. The presentation was given as part of module 3 of a 5-module course on digital preservation tools for repository managers, presented by the JISC KeepIt project. For more on this and other presentations in this course look for the tag 'KeepIt course' in the project blog http://blogs.ecs.soton.ac.uk/keepit/