Oh, the list is probably much longer and includes such things as letters sealed with a kiss, spritzed with perfume, tied with a ribbon and saved for years, pulled out and re-read while you're curled up in a comfy chair by the fireplace...
But, the thing on my mind today is that what we're missing due to e-mails is the "Dear" in our lives. Very few people start out their e-mails with the salutation of "Dear _____." We're lucky if the e-mail even has our name at the beginning. Most e-mails I get start right off with the message.
From the perspective of the writer, I guess the idea is that if it's addressed to a certain person's e-mail address, then they know it's for them. There's no need for the "Dear."
Except that the "Dear" adds a level of civility to correspondence, electronic or otherwise. According to Meriiam-Webster's online dictionary, one meaning of the word dear is "highly valued - often used in a salutation."
I typically start out an e-mail with "Dear ______," especially if it is a first contact. Depending on the response I get and the replies I need to make, further communications may continue with the more formal "Dear _______" or they may become more casual with only only the recipient's name at the beginning of the e-mail. In the interest of brevity, some quick answers may not have a salutation or name at all, but that is usually after several e-mails have already been exchanged.
Of course, if e-mails don't start out with "Dear _____," they certainly don't end with "Love, _______" or even "Sincerely, __________," but that's another blog post.
Happy Letter Writing!