The concept of treatment, as used in psychotherapy, is borrowed from the medical model; it implies a process in which a practitioner does something to a patient with the goal of effecting a cure. 
Many offline psychotherapeutic techniques require that a practitioner be in a position to fine-tune the intervention in a flexible manner as dictated by ongoing, real-time feedback from the patient. While this degree of control is commonplace in a
face-to-face setting, it is beyond the reach of email-based interactions, making it misleading to use the term "treatment" to characterize the process of e-therapy.
The concept of education, particularly student-centered education, implies a gradual process through which a student actively selects and aquires knowledge through learning and instruction. In such a process, the educational provider is a resource that the student, or consumer, draws upon, as desired... much like the World Wide Web and therapuetic email exchanges.
Both treatment and education offer benefits to the consumer. One significant way they differ, however, is in the degree of autonomy the consumer retains. We might imagine an autonomy continuum. At one extreme is pure treament in which the practitioner has complete control of the process; at the other extreme is distance learning in which the student, or consumer, has almost complete control of the educational process. Neither face-to-face nor email therapy is at an extreme along this continuum. But email therapy encourages greater e-client autonomy and includes a stronger presence of education-like attributes, while many face-to-face therapies are more treatment oriented.
Consider your needs, skills, and preferences when deciding which form of therapy is the better choice for you.
Any of us may experience a time in our lives in which we feel fragile or overwhelmed. In times such as these, it is highly desirable to have someone we can turn to, who will nurture and protect us, while we are working through our difficulties. Often, a friend or relative, by being there with a loving heart, can provide us with all that we need. But what if love and acceptance are not enough? Face-to-face psychotherapy has evolved to supply professional expertise should it be required. During such difficult times, a psychotherapist can provide powerful and immediate emotional support as well as appropriate treatment... including a safety net of available emergency interventions. In other words, the face-to-face psychotherapist can step in and help us manage the unmanagable.
On the other hand...
There may also be times in our lives, during which we are neither overwhelmed nor particularly fragile, but nonetheless realize we could be dealing with, and enjoying, life much better than we are. At times like these we can benefit from an educational or coaching process designed to impart knowledge and skills for the care and maintenance of our psychological well-being. In my mind, that's the greatest promise of e-therapy;
not to futilely attempt to replicate what face-to-face psychotherapy already does so well, but rather, to add something new to our toolbox... another option we can use to enhance our lives.