Paul seems disappointed he had been unable to visit Thessalonica in person. Instead, he sent Timothy who returned with a good report that was very encouraging to Paul.
With the communications technology available to us today, it is difficult to imagine waiting for hand-written letters to be walked between cities in order to find out how things are going. On a positive side, keeping in touch required real effort and demonstrated a genuine interest. Are there people you put forth an effort to encourage today? Hundreds of online friends is not the same as investing your life in specific people and having people invest in you.