Here is some info regarding this issue of NT Canon:
“A canonical book had to give either INTERNAL or EXTERNAL evidence that it was divinely inspired (2 Pet 3.16-17; Col 4.16; 1 Thes 5.27; 1 Tim 4.13). If the book was not regarded as canonical by the Church Fathers it was regarded as suspect. If the book failed to claim divine authorship, it was suspect. Between 70 to 170 AD the books of the New Testament were collected, bound together, and were informally circulated as canon. Between 170-303 AD these books were seriously researched by the Church to determine if they met the strict standards of canonicity. Between 303-397 AD the Church held a number of “councils” where books were rejected, and the New Testament you see today was universally recognized as “Scripture”. At first the books of 2 John, 3 John, Jude, and James were disputed as canon, but were finally accepted as God’s Word. The books that were rejected were The Gospel of Mary, The Protevangelion, The First Gospel of the Infancy of Christ, Thomas’s [sic] Gospel of the Infancy of Christ, The Gospel of Nicodemus, The Epistle of Paul to the Laodiceans, The Epistles of Paul the Apostle to Seneca, The Acts of Paul and Thecla, The Epistle of Clement to the Corinthians, The General Epistle of Barnabas, The Epistle of Ignatius to the Ephesians, The Epistle of Ignatius to the Trallians, The Epistle of Ignatius to the Romans, to name a few. All of the rejected books showed some merit, but fell short, in the Churches estimation, of being canonical. Several of the books are still disputed today. For instance, the Epistle of Paul to the Laodiceans is highly esteemed by our Quaker brethren and they pled for its inclusion as canon (Poole’s annotations on Col vi. 16). However, the Church rejected these writings as “spurious” or forgeries, works that would not be accepted into the canon of known Scripture.”
“The decision to exclude books from the canon was not taken lightly. The Councils of Laodicea (363 AD), Damascus (382 AD), Carthage (397 AD) and Hippo (North Africa, 419 AD) all examined and then, after much prayer, accepted or rejected books as New Testament canon.”
This information can be found at:
bibleteacher.org/Dm090_12.htm
Also included is information on what “Canon” means, why have a Canon of Scripture, etc.
The Epistle to the Laodiceans was a brief letter (one chapter), claiming to be written by Paul, and was eventually determined to be a forgery. It and others (NT & OT) were included in some versions of the Vulgate. Those books that remain have stood the test of time (much study and questioning), and are accepted by the church as Scripture.