As with Hebrews, for me the best response is that answering those questions doesn’t matter, though I assume that Ephesians was written by Paul. The book is from early Christianity (approximately 62 AD at the latest, if written by Paul). It was either written by Paul or someone reasonably familiar with his teaching.
For a variety of reasons most New Testament scholars do not believe that this book was ever an actual letter written to a specific Christian congregation in Ephesus. For one thing, the words “to the Ephesians” in verse 1 is not part of the best manuscripts. Instead of a letter, it appears to be a treatise written as if it were a letter. A significant number of scholars, though perhaps not a majority, also question whether the book was written by Paul.
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