A Sunderland woman was bombarded with up to eight letters per day when she broke up with her boyfriend who was serving a sentence behind bars.
Anthony Whittle penned a total of 312 pages, posted in 76 separate letters, from his cell at Durham jail after his girlfriend dumped him by post when he got locked up for violence.
Newcastle Crown Court heard the victim ignored his jail cell ramblings and phone calls, which included a voice mail message threatening to break her jaw, along with the warning "if you won't speak to me you won't speak to no-one".
The 30-year-old had also warned "when I get out of prison I'm going to make your life ******* hell".
Whittle, of no fixed address, admitted putting a person in fear of violence with the harassment campaign between July and October last year.
He confessed he had heard rumours that the woman had started seeing someone else, which was "driving him mad" and sparked his bad behaviour.
Prosecutor Rachel Masters told the court Whittle had been in a relationship with his victim, who lived on Wearside, for five years and had served a six month prison sentence for attacking her in 2013.
Despite him having a restraining order which meant he should stay away from her, the couple reunited after he was released.
It was in April last year Whittle was locked up again, this time for 18 months for assaulting someone else and his girlfriend decided to break up with him "by letter".
Miss Masters told the court: "The defendant responded with letters and phone calls, of which there were numerous."
The court heard the phone calls came so often that the woman got to the point where she let the answering machine pick up.
Miss Masters added: "The letters became more frequent. She describes on one day there were eight letters in a single day."
The court heard when the victim stopped reading the letters and just put them to one side, Whittle started writing on the envelopes to ensure she would see what he had to say.
Judge Tim Gittins jailed Whittle, of no fixed address, who has 50 previous offences on his record, for four months.
The judge told him: "She decided, as was her right, to break off the relationship while you were in custody.
"I appreciate you would have found that particularly difficult but if you were seeking to communicate how much you cared for her and how much you wanted to be with her, you went about it by a very odd route.
"You sent her voicemails, such that she was fearful of picking up the phone and sent her letters, up to eight a day, which were obsessive in nature, a total of 76.
"They no doubt expressed your feelings for her in strong terms but also, it is clear, gave rise to her fearing you were threatening violence towards her as and when you became released."
The court heard the couple have since "patched up" their relationship and the victim no longer supported the prosecution.
Whittle had been released from the jail term after the harassment campaign but has since been recalled over a breach of curfew.
Alec Burns, defending, said Whittle has made efforts to improve himself while serving his sentence and realises how wrong his behaviour was during the relationship break down.
Mr Burns added: "He was literally being driven made by it because he had nothing else to think about while he was in prison.
"There is hope they will move into a house together, away from their normal area, so they can settle down and have a new start."