The email at the centre of the political controversy surrounding the Tánaiste was found by the Department of Justice a fortnight ago.
This is a full week before Tánaiste Frances Fitzgerald was told that the email had been unearthed.
The Taoiseach found out about the contents of the email last Monday night.
This email sets out the legal strategy that was initially set to be pursued against Garda whistleblower Sergeant Maurice McCabe at the O'Higgins Commission in May 2015.
The Tánaiste says she cannot remember reading it when it was first sent to her office on the evening of 15 May 2015.
The Department of Justice confirmed tonight that the email was found on 9 November as part of a search of records in response to a parliamentary question.
This question was one of a series asked by Labour TD Alan Kelly.
The Department said once the email was found a legal view was sought in the context of the Disclosures Tribunal and a trawl started to identify any other relevant records.
A spokesperson said the email was subsequently brought to the attention of the Tánaiste and also the Minister for Justice Charlie Flanagan.
The email was forwarded to the Disclosures Tribunal on Tuesday last.
The Tánaiste distributed a transcript from the email to members of the Dáil last night as she outlined the timeline in relation to its discovery.
Ms Fitzgerald told the House that she was informed about the emails discovery on Thursday 16 November.
This evening the Tánaiste told the Seanad she has received fresh legal advice from the Attorney General which reaffirms that she could not intervene in the legal strategy of the former garda commissioner.