What does Jeremiah 29:3 mean?

He sent the letter with Elasah son of Shaphan and Gemariah son of Hilkiah, whom Zedekiah king of Judah sent to Nebuchadnezzar king of Babylon. The letter said: Jeremiah 29:3 - Modern Text Bible

(Jeremiah's letter is delivered by trusted messengers, showing its official and urgent nature.)