The Epistle to the Ephesians is, in many ways, the crowning glory of the New Testament. But perhaps this letter ought not to be called "Ephesians" for we do not really know to whom it was written. The Christians at Ephesus were certainly among the recipients of this letter, but undoubtedly there were others. In many of the original Greek manuscripts there is a blank where the King James translation has the words "at Ephesus;" just a line where the names of other recipients were apparently to be filled in. That is why the Revised Standard Version does not say, "To the saints at Ephesus," but simply "To the saints who are also faithful in Christ Jesus..."
In Paul's letter to the Colossians there is a reference to a letter he wrote to the Laodiceans. Our Bible does not include an epistle called "A Letter to the Laodiceans," but many have felt that it is the same one we call "The Letter to the Ephesians." The reason is that the Revelation of John (the last book in the Bible) begins with letters to the seven churches of Asia, the first being to Ephesus and the last to Laodicea.
These cities were grouped in a rather rough circle in Asia Minor, and it evidently was customary for anyone who wrote to one of the churches to have the letter sent along to each of the others in turn, continuing around the circle until it came at last to the church at Laodicea. This may account for what would otherwise seem to be a lost letter from the Apostle Paul to the Laodiceans. At any rate, this letter sets forth, in a marvelous way, what no other book of the New Testament describes so completely -- the nature of the body of Christ, the true Church.