The opening verse of Ephesians lacks “in Ephesus” is some important ancient manuscripts (see ESV textnote). Some wonder if the letter to the Ephesians might be Paul’s letter “to the Laodiceans” (Col 4:16), this being the copy of it sent to the church at Ephesus. Since Paul suggested that the church at Colossae read the letter to the Laodiceans perhaps he intended it to be circulated amongst various regional churches.   See Bruce M. Metzger, A Textual Commentary of the Greek New Testament, 2nd ed. (United Bible Societies, 1994), 532.