Apocryphal epistles are generally pseudonymous and were written either by Jews relating to the Old Testament (Letter of Jeremiah) or people focusing on New Testament figures and places.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. Old Testament and New Testament Apocrypha by R. K. Harrison, Page 89-93.)
List
- Abgarus and the Letters of Christ
- Epistle of the Apostles
- Epistle of Barnabas
- Third Corinthians, III Corinthians
- Epistle to the Laodiceans
- Epistle of Lentulus
- Epistles of Paul and Seneca
- Epistle of Titus
Liberal scholars consider 2 Peter and Jude to be apocryphal.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. Old Testament and New Testament Apocrypha by R. K. Harrison, Page 93.)