Email has become overloaded as users make use of email tools for performing a wide range of activities. Previous studies have demonstrated the different strategies employed by email users to manage messages. However, we have little information regarding how to explain those differences between users. The research described in this paper seeks to gain understanding of individual differences in email behaviour. We present results from a questionnaire-based study, which focused on how email users dealt with messages that relate to future tasks or events. We identified two types of user, defined by how they dealt with such messages: the cleaners and the keepers. The difference between these two groups can be attributed to differences in email experience and requirements for flexibility of closure. The ultimate goal of such research is to be able to predict differences in email use and to inform email user interface design and we discuss possible ways in which this could be done. Categorie...