Clustering E-Mails for the Swedish Social Insurance Agency - What Part of the E-Mail Thread Gives the Best Quality?

We need to analyse a large number of e-mails sent by the citizens to the customer services department of a governmental organisation based in Sweden. To carry out this analysis we clustered a large number of e-mails with the aim of automatic e-mail answering. One issue that came up was whether we should use the whole e-mail including the thread or just the original query for the clustering. In this paper we describe this investigation. Our results show that only the query and the answering part should be used, but not necessarily the whole e-mail thread. The results clearly show that the original question contains more useful information than only the answer, although a combination is even better. Using the full e-mail thread does not downgrade the result.