As a high school English teacher for almost 40 years, I have to say I think e-mail is a fabulous invention. Just as the top readers I taught were kids who early fell in love with reading, and read everything they could find, my top writers were kids who did a lot of writing just for fun. They wrote poems in chemistry class, and notes to their friends in all of their classes.
E-mail is this kind of daily bread-and-butter writing, just as reading newspapers or John Grisham is daily bread-and-butter reading. People who are avid e-mail writers develop a fluency and voice and style that spills over to their more formal writing.
And practically, it’s wonderful to have so much information (reservations, directions, times to meet, etc.) in an easily searchable e-mail database rather than in an overflowing file cabinet or hastily scribbled notes.