You are correct that the wording of the guide speaks to regular mail... but you have to know that those words were originally written back in 1997... the virtual Dark Ages insofar as email communications were concerned. Certainly today much of the research and communication can and should be done via the Internet. Today we can learn far more about a program than ever before, partly through the multiplicity of official resources (department websites, brochures, visits) and partly through the informal network (student websites, discussion groups, professor postings online, etc.) Certainly make use of the new contact aids, particularly email. Many professors prefer email, and it is the rare (and out of touch) ones who might find this even the little bit offputting. For speed, brevity, and simplicity, email is definitely to be preferred over snail mail.