BDSM, professor and student, they text each other online about bdsm and erotica anonymously before they know each other

[Monika1871997]

The book has the word "midnight" in it somewhere. They text or mail each other and discuss about their fantasies and bdsm and stuff. Then they get to know that they are professor and student. The professor is a dominant.

It is a romantic erotica with a HEA. I haven't read the book, just read the synopsis. The setting of the book is modern. Book must be written sometime around 2005 to 2015