1 Corinthians 16:21

The salutation of me Paul with mine own hand (KJV)

Then: Paul took over from Sosthenes, the amanuensis (letter writer), in order to let the Corinthians know how much he cared.

Now: Most of the time people use email or type-face letters, but at the bottom of a card or letter, people add an extr a hand written note. This makes it personal and is the part that is always read.