Is communication via personal e-mail between a man and a woman considered a shar'i seclusion (khalwa), even if the interaction is brotherly?

The communication of a man and a woman via email is not considered an unlawful khalwa (private seclusion). However, it is only permissible when there is a need or necessity, and on condition of adhering to the Islamic guidelines in speech, not delving into matters that incite desires, and limiting it to the extent of the need. As for exceeding that to engaging in friendly conversation and companionship, it is forbidden due to the fitna (temptation) involved. Moreover, a man taking a female friend whom he consults or who consults him is not considered a valid need; rather, it is prohibited and forbidden as a means of blocking pretexts (to sin).