“A combination of philological, rhetorical, theological, and historical evidence has led most scholars to conclude that Paul did not write all letters attributed to him.
Nearly all scholars consider Romans, 1 and 2 Corinthians, Galatians, Philippians, 1 Thessalonians, and Philemon as authentic.
Conversely, most would agree that Paul did not write 1 and 2 Timothy or the letter to Titus (the so-called Pastoral Letters), although a few scholars maintain that these letters are also authentic.
With regard to Ephesian, Colossians, and 2 Thessalonians there is an ongoing discussion regarding authorship, but most scholars think that Paul did not write Ephesians, and the same is the case for Colossians. The authorship of 2 Thessalonians is still an open question.
Thus the Pauline letters may be divided into three groups
(a) almost certainly genuine letters (authentic)
(b) letters concerning which there is an ongoing discussion (disputed)
(c) letters almost certainly not written by Paul (pseudonymous or deuteropauline)”