Forster is escorted from the court after being convicted
Dr James Forster, 68, sent a barrage of obscene letters to residents of the picturesque village of Manfield, between 1987 and 1999.
After an eight-day trial at Teeside Crown Court, a jury took four-and-a-quarter hours to find him guilty of three counts of threatening to destroy property, three of sending indecent mail, and one of incitement to commit burglary.
He was cleared of three charges of damaging neighbours' property.
He also ordered health assessments to be carried out on Forster and his sick wife Elizabeth.
The judge told Forster: "I must make it clear to you that the fact that I am granting you bail and the fact that I am seeking reports on you should not be taken by you as giving any indication as to the sentence you are likely to receive.
"All sentences, including a sentence of imprisonment remain an option in this case."
Legal advice
Shirley Dodd, whose son Jeremy, then aged 11, was first accused of being the poison pen letter writer and who herself received up to eight obscene letters, said she was considering whether to sue Forster.
"I'll be talking to somebody legal about this," she declared.
Forster, of Kirklea, Grunton Lane, had denied all 10 charges and claimed he too had been a victim of the hate mail.
The court heard how he:
The mystery of who was behind the hate campaign baffled village residents, but the white-haired pensioner is said by police to have displayed "total defiance" when the trail led to him.
On one occasion, he was asked by officers to look at documents.
But it was only after a while that he realised he was not using his reading glasses, possibly with the intention of claiming at a later date that he had not had been able to see what he was shown.
Police believe Forster tried every trick in the book to disrupt the inquiry.
Some of the letters had been printed and he was asked whether he had a dot matrix printer, which he denied.
It later emerged that he did not own a printer - but he had been lent one by the Open University.
Forster was employed by the National Coal Board for 11 years before attending Kings College at the University of Newcastle upon Tyne.
There, he studied for a BSc in applied sciences before taking an MSc and PhD.
He then lectured at Nottingham University for five years before joining the Open University (OU).
The respected academic rose through the ranks from staff tutor to senior lecturer between 1971 and 1998, including a spell as acting deputy regional director in 1995.
In a statement, regional director of the Open University in the north John Shipley said: "The allegations against Dr Forster have been explained to me, but they do not fit the character of the man I know."