The following patristocrat-style cryptogram was sent to a guy named John. Therefore, it probably begins with "Dear John." You don't know anything more than that, except his romantic relationship has not been going well recently. Please try to recover the plaintext. The ciphertext has the letters grouped into sets of five, for ease of transmission.
Strength of Hint: 517 out of 1000
A joint project of Brendan Bard, Prof. Gregory Bard, and Prof. Seth Dutter, University of Wisconsin---Stout (January 30th, 2019)