A college teacher has been suspended after students saw an "explicit" email displayed on a classroom teaching aid.
The adult-themed message appeared on an interactive whiteboard during an A-level sociology class at Vision West Nottinghamshire College in Mansfield on Tuesday.
The college offered its "sincerest and unreserved apologies" to the students and their parents and guardians.
It said the private email was thought to be intended for the tutor's partner.
The teacher involved has been told to stay away from the college while an investigation is conducted.
Andrew Cropley, the college's principal and chief executive, said: "A private email from a tutor, containing explicit content intended for another adult - believed to be his partner - was inadvertently displayed on a smartboard and seen by students.
"Clearly, this was wholly inappropriate conduct that fell significantly below the high professional standards expected of all our staff.
"I have written to the students and their parents and guardians to offer my sincerest and unreserved apologies."
Mr Cropley added this was an "isolated incident" that does not reflect the daily behaviour and conduct of staff.