It is probably worth mentioning that Paul’s command in Col. 4.16 to have his letter read in neighboring churches was somewhat different than a pure personal correspondence between individuals. The Colossian and Laodicean churches were located on a major trade route (an extension of the Silk Road), and were wealthy (see Rev. 3.17). I think it unusual for them to have circulated the original document because they had the means to have copies made. The letter mentioned in Col. 4 is probably “Ephesians.” If Paul thought the contents so important to share them with another church, then the work is probably providentially preserved. On the basis of internal evidence, the book “Ephesus” doesn’t sound like the place Paul ministered to for nearly 3 years. It does sound like a place he just passed through before his longest time at Ephesus. Laodicea was about 100 miles east of Ephesus so it would have been appropriate to say: For this reason, ever since I heard about your faith in the Lord Jesus and your love for all God’s people (Eph. 1.15 NIV).

The Oxyrhynchus Papyri and The Titles to Paul’s Letters — The Textual Mechanic