With the steady increase in the number of Internet users, email remains the
most popular and extensively used communication means. Therefore, email
management is an important and growing problem for individuals and
organizations. In this paper, we deal with the classification of emails into
two main categories, Business and Personal. To find the best performing
solution for this problem, a comprehensive set of experiments has been
conducted with the deep learning algorithms: Bidirectional Long-Short Term
Memory (BiLSTM) and Attention-based BiLSTM (BiLSTM+Att), together with
traditional Machine Learning (ML) algorithms: Stochastic Gradient Descent
(SGD) optimization applied on Support Vector Machine (SVM) and Extremely
Randomized Trees (ERT) ensemble method. The variations of individual email
and conversational email thread arc representations have been explored to
reach the best classification generalization on the selected task. A special
contribution of this paper is the extraction of a large number of additional
lexical, conversational, expressional, emotional, and moral features, which
proved very useful for differentiation between personal and official written
conversations. The experiments were performed on the publicly available
Enron email benchmark corpora on which we obtained the State-Of-the-Art
(SOA) results. As part of the submission, we have made our work publicly
available to the scientific community for research purposes.