This week in 1858, Boston and New York started an experiment, putting official mail collection boxes along the streets so passersby could drop off their outgoing letters. Before that, they had to go to the post office or catch the mail carrier on his route. The new collection boxes were a welcome innovation, and in the ensuing 155 years became a familiar, if lately dwindling, feature at street corners across the country. Today, in spite of ever-growing volumes of e-mail …