When we engage in mindful e-mailing, that recollecting quality of mindfulness is the main one we rely on. The first thing we recollect is that there is a human being on the other end, a human being just like me. The second thing we recollect is this insight that people who receive e-mails unconsciously fabricate missing information about the emotional context of the sender, so we apply the appropriate care and caution.
Email clients should show photo of other person/people while composing new email message to encourage you to think of them as people while doing so.