'Letters' in the Bible

And I say to the king, 'If to the king it be good, letters let be given to me for the governors beyond the River, that they let me pass over till that I come in unto Judah:

And I come in unto the governors beyond the River, and give to them the letters of the king; and the king sendeth with me heads of a force, and horsemen;

Also, in those days the freemen of Judah are multiplying their letters going unto Tobiah, and those of Tobiah are coming in unto them;

also, his good deeds they have been saying before me, and my words they have been taking out to him; letters hath Tobiah sent to make me afraid.