Kyle Sandilands ordered to hand over texts and email exchanges with Jackie 'O' Henderson ahead of Federal Court battle

Kyle Sandilands has been subpoenaed to provide text messages and emails as his former radio co-host Jackie 'O' Henderson prepares to take on ARN in an $82million Federal Court battle.

Sandilands has been ordered to produce communications he exchanged with Henderson, as well as messages and emails concerning her, during the breakdown of their relationship before ARN ended their long-running KIIS FM breakfast show.

The shock jock has also been subpoenaed to appear as a witness in the case, which is expected to go to trial next month.

Henderson is suing her former employer for unfair dismissal, alleging ARN took unlawful 'adverse action' against her after she raised concerns about Sandilands.

The legal action follows the collapse of the pair's professional relationship and the subsequent termination of their reported $100 million, 10-year contracts in March.

Sandilands has already settled his own legal dispute with ARN after launching an $85million lawsuit against the company.

The broadcaster reached a reported $12million settlement with ARN after negotiations with former chief executive Ciaran Davis.

As part of that earlier legal battle, Sandilands provided the Federal Court with a detailed first-person account outlining the deterioration of his relationship with Henderson.

ARN was recently granted permission to rely on that account in defending Henderson's claim.

The company has also been granted access to a court-ordered medical examination Henderson underwent with clinical psychologist Dr Justine Corry, as well as material produced in response to a subpoena issued to Dr Emma Agnew.

Further private communications could also become part of the case.

Henderson's manager Gemma O'Neill and veteran entertainment reporter Peter Ford were both subpoenaed to produce documents more than two weeks ago, with ARN expected to seek access to material they provide to the court.

The evidence could shed further light on the events surrounding the breakdown of Henderson and Sandilands' relationship and the circumstances leading up to ARN's decision to terminate the breakfast program.

Henderson has not reached a settlement with ARN and is preparing to continue with her legal claim, with the matter expected to proceed to trial in the coming weeks.

However, the case could still be resolved before reaching a courtroom, with Sandilands' separate dispute with ARN ultimately ending in a settlement.

The Federal Court proceedings are expected to involve evidence from several key figures involved in the long-running dispute, including Sandilands himself.

Meanwhile, Sandilands was once again absent from his new show on Monday morning, marking his third absence since his program first went to air three weeks ago.

His subscription-only series, Kyle Sandilands Live, began midway through August and has left the host's chair empty twice due to the shock jock's illness. 

Last Thursday, an episode went to air without Sandilands, 55, with staff at first confused about whether he was physically unwell or having a 'mental health day'. 

'Kyle is not with us again this morning, unfortunately,' announced newsreader Brooklyn Ross.

'He's had a tough week, we saw last week, and I'm okay with him taking some time,' Ross continued. 

'I don't know if he might actually be physically sick... I'm just fine if Kyle needs a day.'

Executive producer Jaimee 'Mayo' Blazquez then clarified that the boss was indeed sick, reading out a text he had sent her that morning.

It follows a tough week for the radio star, who was slapped with legal documents live on air on Wednesday. 

Sandilands was dragged into ARN's escalating legal war with his former radio partner Jackie 'O' Henderson after the media giant served him with a subpoena.

The shock jock was handed the papers during his subscription show on Wednesday, in a stunning moment orchestrated by manager Bruno Bouchet.

Sandilands appeared taken by surprise as Bouchet presented him with the subpoena and a notice to produce documents.

The development came just a week after an emotional Sandilands revealed he was left in tears after learning Henderson had been diagnosed with post-traumatic stress disorder.

As Henderson battles her former employer in a lawsuit, her PTSD diagnosis was referenced in a medical report prepared by Dr Jonathan Phillips.

The radio king later expressed his disbelief at allegations contained in court documents, saying they bore little resemblance to his recollection of events and had left him deeply hurt.