How do plaintiffs get emails relating to companies they are suing?

Question

For example in the case of IBM getting sued over age discrimination, the plaintiff somehow got emails showing that upper management instructed his director manager not to transfer him but to fire him. Out of curiosity how is this possible? I'm guessing a subpoena is involved.But what would the requirements for a subpoena be? What's preventing someone from just making up a random accusation and subpoenaing a company?

Emails establish that after Brown notified Langley in December 2015 that he was likely going to lose his job as part of a layoff Langley attempted to apply to other positions within IBM, and another group agreed to hire him in January, while other managers also expressed interest in him. Despite this, all of the moves were blocked by Human Resources...

https://regmedia.co.uk/2020/01/10/langley_v_ibm_dec_order.pdf

How would they know all this?

This article talks about the battle to get evidence in the discovery phase, under what circumstances and conditions must a defendant produce documents?

Answer 1

Discovery

Basically, you ask.

If your opponent thinks your request is out of bounds they object, give their reasons to the judge, you give yours and the judge orders them to produce the evidence or not.

A lot of people think court cases have big “ah-ha” movements when a witness reveals something unknown on the stand. This rarely happens because there are no secrets in litigation - both sides have to clearly explain their case before, usually well before, they go to trial.